D. A. Hopkinson

Bio: D. A. Hopkinson is an academic researcher from University College London. The author has contributed to research in topics: Isozyme & Population. The author has an hindex of 33, co-authored 81 publications receiving 6250 citations. Previous affiliations of D. A. Hopkinson include University College Hospital.

Developmental changes and polymorphism in human alcohol dehydrogenase

Abstract: Ann. H u m . Genet., Lond. (1971), 34, 251 Printed in Great Britain Developmental changes and polymorphism in human alcohol dehydrogenase BY MOYRA SMITH, D. A. HOPKINSON AND HARRY HARRIS M.R.C. Human Biochemical Genetics Unit, Galton Laboratory, University College London I n man, alcohol dehydrogenase (alcohol: NAD oxidoreductase E.C. 1 . 1 . 1 . 1 ) occurs princi- pally in liver, though low levels of activity have aIso been found in lung, kidney and the gastro- intestinal tract (Moser, Papenberg & von Wartburg, 1968). Evidence for at least three distinct isozymes has been obtained by chromatography of liver extracts on CM cellulose (Blair & Vallee, 1966) and also by electrophoresis (Moser et al. 1968; Pikkarainen & Raiha, 1969; Murray & Motulsky, 1970). Von Wartburg, Papenberg & Aebi (1965) reported that certain individuals have an atypical form of alcohol dehydrogenase associated with an increased level of activity. The usual and atypical forms of the enzyme were shown to differ markedly in pH activity curves with ethanol as substrate. The pH optimum for the usual form was found to be pH 10.8 and for the atypical form pH 8.5. The enzymes also differed in the relative rates at which they oxidized various other alcohols, and in the degree of inhibition produced by various metal binding agents. On the other hand no significant differences were observed in Michaelis constants for the substrates ethanol or acetaldehyde or for the corresponding coenzymes NAD or NADH. Also the pH activity curve with acetaldehyde as substrate was essentially the same for both enzymes, having an optimum at pH 6.0-6.5. A simple screening test to distinguish the usual from the atypical enzyme in crude liver homo- genates was designed (von Wartburg et al. 1965). This involves determining the ratio of the activity at pH 11.0 to that at pH 8-8 with ethanol as substrate under standard conditions. The usual enzyme gives a value for this ratio greater than 1.0, and the atypical enzyme less than 1.0. In a survey of 59 liver samples from different individuals in Switzerland, 12 were found to have the atypical alcohol dehydrogenase, and in another series of 50 individuals from London, 2 were found to be atypical (von Wartburg & Schiirch, 1968). The atypical enzyme occurred in indi- viduals varying from 16 to 82 years of age. Pikkarainen & Raiha (1967) reported that alcohol dehydrogenase activity in liver is low during foetal life and reaches adult levels about 5 years after birth. Changes in electrophoretic pattern have also been noted during development (Pikkarainen & Raiha, 1969; Murray & Motulsky, 1970). In the earliest stages only a single isozyme is observed but later further iso- zymes appear. I n adult liver individual variations in the relative contribution of the different isozymes to the total activity have been noted (von Wartburg & Schiirch, 1968), but no clear electrophoretic differences between the usual and atypical alcohol dehydrogenases as determined by the ratio of activity at pH 11.0 and pH 8.8 were detected. The present paper is concerned with a study of human alcohol dehydrogenase in which liver, lung, kidney and intestinal material from foetuses, infants and adults has been examined. The en- zyme has been investigated both by spectrophotometric assay at different pH’s and by starch-gel

Inherited variations in human phosphohexose isomerase.

Abstract: SUMMARY 1. The elctrophoretic pattern of phosphohexose isomerase has been examine in the blood of 3397 unrelated individuals from several different populations groups. 2. Eight variant phenotypes were identinfied and these were designated PHI 2-1, 3-1, 4-1, 5-11 6-1, 7-1, 8-1, 9-1. All of these were rare in the populations studied except the variant designated PHI 3-1, which was observed with a frequency of about 1% in a mixed population of Asiatic Indians. 3. Studies of selected families indicated that the variants occured in individuals who are heterozygous for one or another of a series of rare alleles at an autosomal locus. 4. Studies on the family of a patient that the patient was heterozygous for two different rare alleles at the PHI locus, each associated with reduced PHI activity. The patinet's mother showed the PHI 9-1 phenotype and his father showed a new phenotype designated PHI 10-1. The patient's phenotype has been designeated PHI 9-10. 5. The enzyme appears to be a dimer and in heterozygotes isozymes of hybrid submit compostion as well as isozymes of like subunit compostion are apparently formed.

Further data on the adenosine deaminase (ADA) polymorphism and a report of a new phenotype

Abstract: In a study of human red cell adenosine deaminase (ADA) three different types of isozyme patterns were identified (Spencer, Hopkinson & Harris, 1968). One phenotype designated ADA 1 was found in about 89 % of the English population, the second phenotype, ADA 2-1, was found in about 11 yo of the population and the third phenotype, designated ADA 2, was seen only once in a survey of 580 unrelated English people. Sixty-seven families were studied and the family data suggested that the three ADA phenotypes were determined by two autosomal alleles ADA1 and ADA2; phenotypes ADA 1 and ADA 2 corresponding to the homozygous genotypes ADAlADAl and ADAaADA2 respectively and phenotype ADA 2-1 corresponding to the heterozygous combination ADA1ADA2. This paper contains further family data and more extensive population data on the ADA polymorphism and also a description of a new phenotype.

Average heterozygosity per locus in man: an estimate based on the incidence of enzyme polymorphisms

Abstract: SUMMARY 1. Data from electrophoretic surveys of enzymes in European populations are reviewed. 2. Out of the seventy-one structural gene loci determining enzyme structure which have been scrutinized electrophoretically, 20 (28 %) were found to show genetic polymorphism. The average heterozygosity per locus for alleles determining electrophoretic variants is estimated at 0·067. 3. These results are compared with data from some other species. 4. For several different reasons, most of which relate to the techniques used and the enzymes and tissues surveyed, it seems likely that the present data considerably underestimate the true incidence of polymorphism and average heterozygosity per locus.

Construction of a genetic linkage map in man using restriction fragment length polymorphisms.

Abstract: We describe a new basis for the construction of a genetic linkage map of the human genome. The basic principle of the mapping scheme is to develop, by recombinant DNA techniques, random single-copy DNA probes capable of detecting DNA sequence polymorphisms, when hybridized to restriction digests of an individual's DNA. Each of these probes will define a locus. Loci can be expanded or contracted to include more or less polymorphism by further application of recombinant DNA technology. Suitably polymorphic loci can be tested for linkage relationships in human pedigrees by established methods; and loci can be arranged into linkage groups to form a true genetic map of "DNA marker loci." Pedigrees in which inherited traits are known to be segregating can then be analyzed, making possible the mapping of the gene(s) responsible for the trait with respect to the DNA marker loci, without requiring direct access to a specified gene's DNA. For inherited diseases mapped in this way, linked DNA marker loci can be used predictively for genetic counseling.

The glutathione S-transferase supergene family: regulation of GST and the contribution of the isoenzymes to cancer chemoprotection and drug resistance.

Abstract: The glutathione S-transferases (GST) represent a major group of detoxification enzymes. All eukaryotic species possess multiple cytosolic and membrane-bound GST isoenzymes, each of which displays distinct catalytic as well as noncatalytic binding properties: the cytosolic enzymes are encoded by at least five distantly related gene families (designated class alpha, mu, pi, sigma, and theta GST), whereas the membrane-bound enzymes, microsomal GST and leukotriene C, synthetase, are encoded by single genes and both have arisen separately from the soluble GST. Evidence suggests that the level of expression of GST is a crucial factor in determining the sensitivity of cells to a broad spectrum of toxic chemicals. In this article the biochemical functions of GST are described to show how individual isoenzymes contribute to resistance to carcinogens, antitumor drugs, environmental pollutants, and products of oxidative stress.A description of the mechanisms of transcriptional and posttranscriptional regulat...

Methods of multilocus enzyme electrophoresis for bacterial population genetics and systematics

Abstract: Methodes d'extraction d'enzymes, d'electrophorese en gel et de coloration specifique des enzymes utilisees pour etudier la variation genetique chez Escherichia coli et d'autres bacteries. Les procedures decrites peuvent s'appliquer, avec quelques modifications mineures, a toute espece de bacterie