1. An enzyme from rat liver, catalysing 3alpha-hydroxy steroid-dependent NAD(P) transhydrogenation and NAD-linked and NADP-linked dehydrogenation of 3alpha-hydroxy steroids, has been purified 100-fold by chromatography on DEAE-cellulose and calcium phosphate gel. 2. No separation of these activities into different protein fractions has been achieved. 3. The properties of the enzyme in catalysing NAD-linked and NADP-linked dehydrogenation have been compared, with androsterone as substrate. Differences were found in pH optima, affinity for coenzyme and steroid, equilibrium constants and effects of salts. 4. NAD-linked dehydrogenation is inhibited by NADPH(2) but is protected from this inhibition by chloride, which alone is itself an inhibitor. 5. The relevance of these findings to the problem of the number of enzymes involved in catalysis of 3alpha-hydroxy steroid-dependent transhydrogenation is discussed.

Androsterone↗

PubMedDate not supplied

Human brain: aldehyde dehydrogenase activity and isozyme distribution in different areas.

Three human post-mortem brains were dissected into seventeen areas and assayed for aldehyde dehydrogenase (EC 1.2.1.3) activity employing two assay systems: one at 68 microM and another at 13.6 mM propionaldehyde. The levels of activity with 68 microM propionaldehyde were significantly higher in cerebellum and putamen. The same brain areas were also examined by isoelectric focusing. By this procedure two distinct bands of aldehyde dehydrogenase activity (the cytoplasmic E1 and mitochondrial E2) could be readily visualized in cerebellum and putamen while other brain areas contained mainly the mitochondrial E2 isozyme.

Aged↗

PubMedDate not supplied

Aldehyde dehydrogenase content and composition of human liver.

Human liver contains only four proteins which catalyze dehydrogenation of acetaldehyde; two of these are tetrameric with MW of 220,000 and are structurally related. These enzymes were purified previously to homogeneity and are now known as the cytoplasmic E1 and mitochondrial E2. The other two proteins do not appear to be structurally related to E1 and E2. The recently isolated E4 enzyme is a dimer of MW of ca. 175,000; the E3 may be a polymorphic enzyme. The Enzyme Commission classification for E1 and E2 is EC 1.2.1.3, that for E4 is at present uncertain since its Michaelis constants for short chain aldehydes are high, making it unlikely that these would be its natural substrates. The relationship between E3 and E4 is also uncertain. Employing a suitably designed assay, E1 and E2 are assayed as "low Km" enzymes while E3 and E4 are assayed as "high Km" enzymes. Therefore by employing such an assay, combined with electrofocusing procedure, an assessment of enzyme content and composition of aldehyde dehydrogenase in human liver can be made.

Acetaldehyde↗

PubMedDate not supplied

Inactivation of aldehyde dehydrogenase in intact rat liver mitochondria by dopamine.

Aldehyde dehydrogenase (EC 1.2.1.3) within isolated rat liver mitochondria was inactivated by incubation with dopamine. Concurrent with this inactivation, incorporation of radioactivity from 14C-labelled dopamine into three mitochondrial matrix proteins (subunit mol.wt. = 120,000; 54,000; 20,000 daltons) occurred. The 54,000 mol.wt. protein also interacted with antihuman mitochondrial aldehyde dehydrogenase antibody. Inactivation of aldehyde dehydrogenase by dopamine occurred more readily in females than in males. Use of monoamine oxidase (EC 1.4.3.4) inhibitors (deprenyl and clorgyline) partially protected against inactivation. Monoamine oxidase catalyzed conversion of to 3,4-dihydroxyphenylacetaldehyde only partially accounted for aldehyde dehydrogenase activity loss.

Aldehyde Dehydrogenase↗

PubMedDate not supplied

Aldehyde dehydrogenase and monoamine oxidase in rat liver mitochondria.

Monoamine oxidase (EC 1.4.3.4) and aldehyde dehydrogenase (EC 1.2.1.3) activities were compared in the liver mitochondria of male and female rats. Monoamine oxidase activity using benzylamine as a substrate was significantly higher in males as compared with females: 1.45 versus 0.74 mumols/mg mitochondrial protein/hr, respectively. Monoamine oxidase activity using tyramine as a substrate and aldehyde dehydrogenase activity were the same in males and females. Monoamine oxidase-tyramine and aldehyde dehydrogenase activities did not vary with the different phases of the estrous cycle in the female but the activity of monoamine oxidase-benzylamine did; rats in the proestrous phase had the highest activity and those in the estrous phase had the lowest.

Aldehyde Dehydrogenase↗

PubMedDate not supplied

Purification and characterization of aldehyde dehydrogenase from rat liver mitochondrial matrix.

Aldehyde dehydrogenase (EC 1.2.1.3) has been purified to homogeneity from Sprague-Dawley rat liver mitochondrial matrix; its specific activity with propionaldehyde (1 mM at pH 9.0) is 1.4 mumol/min/mg. It has a native molecular weight of ca. 260,000 daltons, a subunit weight of 54,000 daltons and separates into two bands on isoelectric focusing (pI, 5.15 and 5.30); its extinction coefficient at 280 nm for 1 mg/ml solution is 1.2 and 280/260 nm ratio is 1.6. The enzyme prefers NAD over NADP as the coenzyme; the Km for NADP (67,000 microM) is three orders of magnitude greater than that for NAD (61 microM); the Km for acetaldehyde is 2 microM and for propionaldehyde is 0.8 microM at pH 7.0. The enzyme is reversibly inhibited by chloral (Ki = 3 microM) but is resistant to disulfiram inhibition. In addition another aldehyde dehydrogenase, first observed in the mitochondrial matrix during isoelectric focusing, has been partially purified. It has a Km for propionaldehyde of 0.7 mM and an isoelectric point of 6.4. Its activity with glutamic-gamma-semialdehyde (Km = 0.13 mM) is ca. 20 times higher than with propionaldehyde identifying the enzyme as glutamic-gamma-semialdehyde dehydrogenase (EC 1.5.1.12).

Aldehyde Dehydrogenase↗

PubMedDate not supplied

Inhibition of human aldehyde dehydrogenase isozymes by propiolaldehyde.

Propiolaldehyde--a metabolite of pargyline (Shirota et al., 1979) can function as an inhibitor or as a substrate of human aldehyde dehydrogenase (EC 1.2.1.3), dependent on conditions. In the presence of high concentration of NAD, propiolaldehyde is a substrate for both the cytoplasmic E1 isozyme and the mitochondrial E2 isozyme. The Km values are comparable to those with other short chain aldehydes; the maximal velocity is also similar for E2 but lower by about three-fold for E1. Preincubation with propiolaldehyde in the absence of NAD produces inactivation with K1 values of 1.6 microM for E1 and 1.8 microM for E2. NAD, but not propanal, protects both isozymes against inactivation with propiolaldehyde.

Aldehyde Dehydrogenase↗