Charles R. Shaw

Retinol and alcohol dehydrogenases in retina and liver

Abstract Isozymes of alcohol dehydrogenase (alcohol: NAD + oxidoreductase, EC 1.1.1.1) and retinol (vitamin A 1 ) dehydrogenase (retinol: NAD + oxidoreductase) were studied in retina and liver extracts of rat by starch-gel electrophoresis. The retina demonstrated two zones of retinol dehydrogenase activity and a separate zone of alcohol dehydrogenase activity. The liver had single zones each of retinol and alcohol dehydrogenase activity, neither of which coincided with the three zones from the retina. It is concluded on the basis of the electrophoretic findings supplemented with inhibition, heat inactivation, and pH studies that these five zones represent five different enzymes, and that vitamin A is oxidized in the retina and the liver by specific and distinct enzymes. Liver-type alcohol dehydrogenase is absent from the eyes and eye-type is absent from the liver.

Hormone-Induced Esterase in Mouse Kidney

Starch-gel electrophoresis of an extract of mouse kidney disclosed that an esterase is present in mature males but absent in females and immature males. When testosterone was injected for 7 days the enzyme could be detected in kidney extracts obtained from both female and young animals. Hence the enzyme may be a hormone-induced one.

Glucose-6-Phosphate Dehydrogenase: Homologous Molecules in Deer Mouse and Man

Two forms of glucose-6-phosphate dehydrogenase, A and B, have been reported in deer mouse tis sues. The B enzyme, which showed autosomally controlled polymorphism, is now found to be equally active to ward glucose-6-phosphate and galac tQse-6- phosphate; the A enzyme is specific for the former. Human and horse livers also have two forms of glucose-6-phosphate dehydrogenase which exhibit the same substrate spe cifities as those in the deer mouse. A wide variety of electrophoretic patterns was seen in the human galactose-active enzyme.

Autosomally Determined Polymorphism of Glucose-6-Phosphate Dehydrogenase in Peromyscus

Glucose-6-phosphate dehydrogenase commonly occurs in at least two forms in most tissues of the deer mouse, Peromyscus maniculatus, as demonstrated by starch-gel electrophoresis. An autosomally determined genetic polymorphism in one of the enzymes was discovered. A hybrid molecule occurs in the heterozygote; this suggests a dimeric structure of this enzyme.

GLUCOSE 6-PHOSPHATE DEHYDROGENASE AND HEXOSE 6-PHOSPHATE DEHYDROGENASE OF MAMMALIAN TISSUES*

Glucose 6-phosphate dehydrogenase (GGPD) is among the most thoroughly studied of the enzymes. I t has been of particular interest to geneticists because it is controlled in man by a gene located on the X-chromosome. Genetic variants in man thus have been very useful markers in studies of the X-inactivation hypothesis (Lyon hypothesis), which states that in the human female, which has two X-chromosomes in each somatic cell, only one of the X-chromosomes is active; the other is in an inactive state. Studies of the G6PD locus have generally confirmed this hypothesis, particularly the demonstration (Davidson et al., 1963) that clones of cells cultured from skin of Negro females heterozygous for a G6PD variant carried either one or the other form of the enzyme, but not both. GGPD, more recently, has been shown to be X-linked also in equine species (Mathai et al., 1966) and in Dmsophila (Young et al., 1964), findings which have led to the speculation that there may be some general advantage in having this enzyme controlled by the X-chromosome. Thus, it was of particular interest when we found a G6PD in the deer mouse, Peromyscus maniculatus, which is autosomally controlled (Shaw & Barto, 1965). However, as noted in our initial report, this enzyme is probably not homologous with the Xlinked enzyme of human erythrocytes. There are two different forms of G6PD in deer mouse tissues, which were arbitrarily designated the A and B forms. The B form is the autosomally controlled type, and does not occur in deer mouse erythrocytes. The A form, which was found in all tissues studied including erythrocytes, was postulated to be homologous with the G6PD of human erythrocytes. Subsequent study has amply confirmed this impression, and the evidences will be reviewed here. A second form of G6PD also was found subsequently in human tissues (Shaw, 1966; Ohno et al., 1966), and this appears to be homologous with the B enzyme of deer mouse. The evidences for this homology will be presented, together with studies of other mammals which indicate that both homologies are rather general throughout the mammalian order, with one interesting exception.

New genetically determined molecular form of erythrocyte esterase in man.

An altered molecular form of erythrocyte esterase was discovered in hemolysates from two males and one female in three generations of the same family. This indicates that the alternate enzyme form is under the control of a single autosomal gene. Evidence suggests that the atypical esterase is a variant form of erythrocyte carbonic anhydrase.

Multiple substrate specificities of some demydrogenase molecules

Abstract A wide variety of enzymes demonstrating dehydrogenase activity has been described. Generally, these have been considered separate and relatively specific enzymes, although several reports of “non-specific” dehydrogenase activities have appeared. For example, Vesell and Bearn (1957) found in zone electrophoresis of human serum that, of four zones of activity, two showed both malate and lactate dehydrogenase activity, while each of the others appeared specific. Struck and Sizer (1960) showed that beef glutamate dehydrogenase (GDH) was active toward a number of other amino acids. Davies and Kun (1957) showed activity of ox heart mitochondrial malate dehydrogenase (MDH) toward several α-keto dicarboxylic acids. This report presents evidence that several dehydrogenase activities, previously considered unrelated, reside in the same molecule. The technique employed was starch gel electrophoresis, with dehydrogenase activity being demonstrated in the gel using nitro blue tetrazolium as the terminal electron acceptor. The evidence for the identity of enzymes acting upon different substrates is based upon the identity of the isozyme patterns, using various tissues from normal animals as well as some with naturally-occurring alterations in electrophoretic patterns.