Aldehyde dehydrogenase 2 (ALDH2) deficiency constitutes one of the most common hereditary enzyme deficiencies, affecting 35% to 40% of East Asians and 8% of the world population. It causes the well-known Asian Alcohol Flush Syndrome, characterized by facial flushing, palpitation, tachycardia, nausea, and other unpleasant feelings when alcohol is consumed. It is also associated with a marked increase in the risk of a variety of serious disorders, including esophageal cancer and osteoporosis. Our recent studies with murine models have (...) demonstrated that a one-time administration of an adeno-associated virus (AAV) gene transfer vector expressing the human ALDH2 coding sequence (AAVrh.10hALDH2) will correct the deficiency state and prevent alcohol-induced abnormalities of the esophagus and bone. If successful in humans, such strategy would reduce the increased risk-associated disorders such as esophageal cancer and osteoporosis, but also prevent the Asian Alcohol Flush Syndrome. This treatment thus raises ethical concerns: although it would potentially prevent fatal disease, it could also allow affected individuals to drink alcohol without suffering the Asian Alcohol Flush Syndrome and, hence, potentially enable personal destructive behavior. Here we explore the ethical arguments against the development of a gene therapy for ALDH2 deficiency and we find them wanting. We contend that development of such treatments is ethically appropriate and should be part and parcel of the solutions offered against the condition. (shrink)

Malignant cells are characterized by an increased content of endogenous formaldehyde formed as a by‐product of biosynthetic processes. Accumulation of formaldehyde in cancer cells is combined with activation of the processes of cellular formaldehyde clearance. These mechanisms include increased ALDH and suppressed ADH5/FDH activity, which oncologists consider poor and favorable prognostic markers, respectively. Here, the sources and regulation of formaldehyde metabolism in cancer cells are reviewed. The authors also analyze the participation of oncoproteins such as fibulins, FGFR1, HER2/neu, FBI‐1, and (...) MUC1‐C in the control of genes related to formaldehyde metabolism, suggesting the existence of two mutually exclusive processes in cancer cells: 1) production and 2) oxidation and elimination of formaldehyde from the cell. The authors hypothesize that the study of the anticancer properties of disulfiram and alpha lipoic acid – which affect the balance of formaldehyde in the body – may serve as the basis of future anticancer therapy. (shrink)

Abstractα/β barrels have an ill‐defined origin. Evidence exists which favours their divergent evolution from a common ancestral barrel and convergent evolution to a stable fold. However, recent sequence and structural information for the flavin oxidase/dehydrogenase family of barrel enzymes indicate that sub‐families of α/β barrels have evolved divergently. The modular fusion of barrel domains with core structures from other gene families has also contributed to the evolution of related but catalytically distinct enzyme molecules within each sub‐family of the flavin (...) oxidases/dehydrogenases. An analysis of the structures and sequences of the flavin oxidases/dehydrogenases has now enabled studies focusing on the evolutionary origins and modular assembly of this important family of proteins to be initiated. (shrink)

Abstract11β‐hydroxysteroid dehydrogenases regulate glucocorticoid concentrations and 17β‐hydroxysteroid dehydrogenases regulate estrogen and androgen concentrations in mammals. Phylogenetic analysis of the sequences from two 11β‐hydroxysteroid dehydrogenases and four mammalian 17β‐hydroxysteroid dehydrogenases indicates unusual evolution in these enzymes. Type 1 11β‐ and 17β‐hydroxysteroid dehydrogenases are on the same branch; Type 2 enzymes cluster on another branch with β‐hydroxybutyrate dehydrogenase, 11‐cis retinol dehydrogenase and retinol dehydrogenase; Type 3 17β‐hydroxysteroid dehydrogenase is on a third branch; while the pig dehydrogenase clusters (...) with a yeast multifunctional enzyme on a fourth branch. Pig 17β‐hydroxysteroid dehydrogenase appears to have evolved independently from the other three 17β‐hydroxysteroid dehydrogenase dehydrogenases; in which case, the evolution of 17β‐hydroxysteroid dehydrogenase activity is an example of functional convergence. The phylogeny also suggests that independent evolution of specificity toward C11 substituents on glucocorticoids and C17 substituents on androgens and estrogens has occurred in Types 1 and 2 11β‐ and 17β‐hydroxysteroid dehydrogenases. (shrink)

The regulation of glucose dehydrogenase (GLD) in Drosophila illustrates the combinatorial aspects of gene regulation in development. Furthermore, the findings serve to point up a general question about cukaryotic structural gene control: is regulation of expression always optimal?

Two enzymes involved in the synthesis of pyrimidine and purine nucleotides, CTP synthase (CTPS) and IMP dehydrogenase (IMPDH), can assemble into a single or very few large filaments called rods and rings (RR) or cytoophidia. Most recently, asymmetric cytoplasmic distribution of organelles during cell division has been described as a decisive event in hematopoietic stem cell fate. We propose that cytoophidia, which could be considered as membrane‐less organelles, may also be distributed asymmetrically during mammalian cell division as previously described (...) for Schizosaccharomyces pombe. Furthermore, because each type of nucleotide intervenes in distinct processes (e.g., membrane synthesis, glycosylation, and G protein‐signaling), alterations in the rate of synthesis of specific nucleotide types could influence cell differentiation in multiple ways. Therefore, we hypothesize that whether a daughter cell inherits or not CTPS or IMPDH filaments determines its fate and that this asymmetric inheritance, together with the dynamic nature of these structures enables plasticity in a cell population. (shrink)

The Earth agglomerates and heats. Convection cells within the planetary interior expedite the cooling process. Volcanoes evolve steam, carbon dioxide, sulfur dioxide and pyrophosphate. An acidulous Hadean ocean condenses from the carbon dioxide atmosphere. Dusts and stratospheric sulfurous smogs absorb a proportion of the Sun’s rays. The cooled ocean leaks into the stressed crust and also convects. High temperature acid springs, coupled to magmatic plumes and spreading centers, emit iron, manganese, zinc, cobalt and nickel ions to the ocean. Away from (...) the spreading centers cooler alkaline spring waters emanate from the ocean floor. These bear hydrogen, formate, ammonia, hydrosulfide and minor methane thiol. The thermal potential begins to be dissipated but the chemical potential is dammed. The exhaling alkaline solutions are frustrated in their further attempt to mix thoroughly with their oceanic source by the spontaneous precipitation of biomorphic barriers of colloidal iron compounds and other minerals. It is here we surmise that organic molecules are synthesized, filtered, concentrated and adsorbed, while acetate and methane—separate products of the precursor to the reductive acetyl-coenzyme-A pathway—are exhaled as waste. Reactions in mineral compartments produce acetate, amino acids, and the components of nucleosides. Short peptides, condensed from the simple amino acids, sequester ‘ready-made’ iron sulfide clusters to form protoferredoxins, and also bind phosphates. Nucleotides are assembled from amino acids, simple phosphates carbon dioxide and ribose phosphate upon nanocrystalline mineral surfaces. The side chains of particular amino acids register to fitting nucleotide triplet clefts. Keyed in, the amino acids are polymerized, through acid–base catalysis, to alpha chains. Peptides, the tenuous outer-most filaments of the nanocrysts, continually peel away from bound RNA. The polymers are concentrated at cooler regions of the mineral compartments through thermophoresis. RNA is reproduced through a convective polymerase chain reaction operating between 40 and 100°C. The coded peptides produce true ferredoxins, the ubiquitous proteins with the longest evolutionary pedigree. They take over the role of catalyst and electron transfer agent from the iron sulfides. Other iron–nickel sulfide clusters, sequestered now by cysteine residues as CO-dehydrogenase and acetyl-coenzyme-A synthase, promote further chemosynthesis and support the hatchery—the electrochemical reactor—from which they sprang. Reactions and interactions fall into step as further pathways are negotiated. This hydrothermal circuitry offers a continuous supply of material and chemical energy, as well as electricity and proticity at a potential appropriate for the onset of life in the dark, a rapidly emerging kinetic structure born to persist, evolve and generate entropy while the sun shines. (shrink)

MacDonald and Kreitman (1991) propose a test of the neutral mutationrandom drift (NM-RD) hypothesis, the central claim of the neutral theory of molecular evolution. The test involves generating predictions from the NM-RD hypothesis about patterns of molecular substitutions. Alternative selection hypotheses predict that the data will deviate from the predictions of the NM-RD hypothesis in specifiable ways. To conduct the test Mac- Donald and Kreitman examine the evolutionary dynamics of the alcohol dehydrogenase (Adh) gene in three species of Drosophila. (...) The test compares the number of DNA sequence changes between species and within species. The number of DNA differences is an indicator of the evolutionary rate of the Adh gene. Based on the test they conclude that there is strong evidence for adaptive protein evolution at particular sites in the gene. Understanding the test requires some basic knowledge about molecular terms and the predictions of neutral theory. The two important terms are fixed differences and polymorphisms. These are determined by comparing DNA sequences made up of thousands of individual nucleotide sites. A site that is unchanged within a species but different from a related species counts as a fixed difference. These are mutations that occur in some common ancestor of the lineage such that all descendants inherit the change. A site that differs within a species counts as a polymorphism. Determining the number of fixed differences and polymorphisms requires placing 1 each individual gene sequence onto a phylogenetic tree. A coalescent tree charts the ancestral relationships for a set of individual gene sequences. Sequences sampled from within a species form a within-species tree. The common ancestors of each within-species tree form a between-species tree. A detected difference counts as a polymorphism or a fixed difference depending on where it occurs in the phylogenetic tree (cf. Table 1). The test uses the numbers of polymorphisms and fixed differences as indicators of evolutionary rates.. (shrink)

We review here some recent data about glucose‐6‐phosphate dehydrogenase (G6PD), the first and key regulatory enzyme of the pentose phosphate pathway. New evidence has been presented to suggest that malaria is a selective agent for G6PD deficiency, which is the most common enzymopathy in man, and that G6PD deficiency, generally considered to be a mild and benign condition, is significantly disadvantageous in certain environmental conditions. At the molecular level, the enzyme structure has recently been elucidated and mechanisms regulating G6PD (...) gene expression have been determined. A G6PD knock‐out mutation introduced in mouse cells makes them exquisitely sensitive to oxidative stress, indicating that this ubiquitous metabolic enzyme has a major role in the defence against oxidative stress, even in eukaryotic nucleated cells, which have several alternative routes for providing the same protection. Because of the high prevalence of G6PD deficiency in many populations, it is expected that these findings will prompt further studies to ascertain the putative role of G6PD deficiency in conditions such as carcinogenesis and ageing. (shrink)

A set of amino acid side chains that confer specificity for the coenzyme NADPH and the substrate glutathione in the flavoprotein disulphide oxidoreductase, glutathione reductase, has been identified. Systematic replacement of these amino acid residues in the coenzyme‐binding site switches the specificity of the enzyme from its natural strong preference for NADPH to a marked preference For NADH. The amino acids replaced all lie in a structural motif within the dinucleotide‐binding domain of the protein. Since this domain is a feature (...) common to most dehydrogenases (reductases) that use nicotinamide coenzymes, it may be that the coenzyme specificities of all such enzymes can be manipulated in this way. Similarly, amino acid residues involved in the selective recognition of trypanothione by trypanothione reductase, an enzyme related to glutathione reductase and exclusive to trypanosomatids, were identified. Suitable mutation of the corresponding residues in E. coli glutathione reductase switched its substrate specificity towards trypanothione. A better understanding of the substrate specificity of these enzymes could open up a route to the chemotherapy of trypanosomal infections. (shrink)

Parkinsonism (PD) is a neurodegenerative disorder of the brain resulting in dopamine deficiency caused by the progressive death of dopaminergic neurons. PD is characterized by a combination of rigidity, poverty of movement, tremor and postural instability. Selegiline is a selective and irreversible propargylamine type B monoamine oxidase (MAO‐B) inhibitor. This drug, which inhibits dopamine metabolism, has been effectively used in the treatment of PD. However, its therapeutic effects are compromised by its many neurotoxic metabolites. To circumvent this obstacle, a novel (...) MAO‐B inhibitor, rasagiline, was developed. Paradoxically, the neuroprotective mechanism of propargylamines in different neuronal models appears to be independent of MAO‐B inhibition. Recent investigations into the neuroprotective mechanism of propargylamines indicate that glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH), MAO‐B and/or other unknown proteins may represent pivotal proteins in the survival of the injured neurons. Delineation of the mechanism(s) involved in the neuroprotective effects exerted by MAO‐B inhibitors may provide the key to preventive novel therapeutic modalities. BioEssays 26:80–90, 2004. © 2003 Wiley Periodicals, Inc. (shrink)

In earlier work we have described how computer algebra may be used to derive composite rate laws for complete systems of equations, using the mathematical technique of Gröbner Bases (Bennett, Davenport and Sauro, 1988). Such composite rate laws may then be fitted to experimental data to yield estimates of kinetic parameters.Recently we have been investigating the practical application of this methodology to the estimation of kinetic parameters for the closed two enzyme system of aspartate aminotransferase (AAT) and malate dehydrogenase (...) (MDH) (Fisher 1990a; Fisher 1990b; Bennett and Fisher, 1990). (shrink)

Recent work has led to the discovery of six patients with 4‐hydroxybutyric acid‐uria, a severe hereditary human pathology characterized by the accumulation of a compound of known neuropharmacologic activity in body fluids. The enzymatic deficiency has been localized to succinic semialdehyde dehydrogenase, one of two enzymes involved in the metabolism of the neurotransmitter GABA. The disease is inherited as an autosomal recessive trait, and carrier detection has been accomplished by quantification of intermediate enzyme activities. The clinical, enzymatic and pharmacologic (...) characteristics of this disease are reviewed here. (shrink)

Defects in man in four steps of 4‐aminobutyric acid (GABA) metabolism may interefere with the function of this major inhibitory neurotransmitter. Glutamic acid decarboxylase, 4‐aminobutyric acid aminotransferase, succinic semialdehyde dehydrogenase, and homocarnosinase are closely identified with the brain, but two of these enzymes are expressed in cultured peripheral cells, which may permit novel approaches to the study of the metabolism and regulation of GABA.

Maize develops separate male and female flowers in different locations on a single plant. Male flowers develop at the tip of the shoot in the tassel, and female flowers develop on the ears, which terminate short branches. The development of male flowers in tassels and female flowers in ears is the result of selective abortion of pistils or stamens, respectively, in developing florets. Genetic analysis has shown that stamen abortion and pistil abortion are under the control of two different genetic (...) pathways. Local levels of the plant hormone gibberellic acid determine whether or not stamens are suppressed. Pistil abortion is under the regulation of the tassel seed genes, one of which has been shown to encode a short‐chain alcohol dehydrogenase. The tassel seed genes play a role in regulating the fate of inflorescence meristems as well as pistil primordium fate. (shrink)