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Biomedical subjects

D A Hopkinson

Publications and source records attributed to D A Hopkinson.

At least 91 records · Page 5Linked to original sources
PubMed1980

Human FAD-dependent NAD(P)H diaphorase.

A newly discovered human diaphorase, designated diaphorase-4, which accounts for a major part of the diaphorase activity of most tissues but does not occur in erythrocytes, is described. In contrast with other human diaphorases, it is dependent on FAD for activity after electrophoresis, inhibited by low concentrations of dicoumarol and shows a marked affinity for Cibacron Blue. The molecular weight was estimated to be 49000 +/- 1800 by gel filtration. Diaphorase-4 appears to show person-to-person quantitative variation, so that about 4% of the population lack appreciable enzyme activity, but it is not yet clear whether this variation is of genetic or non-genetic origin.

Anthracenes↗
PubMed1980

Changes in the activity and isozyme patterns of glycolytic enzymes during stimulation of normal human lymphocytes with phytohaemagglutinin.

A study has been made of the effects of phytohaemagglutinin on the gene expression of the glycolytic enzymes in cultured human lymphocytes. All the enzymes were found to show an average increase in activity of between 160% and 360% in stimulated cells, but the increases were greater for the enzymes comprising the second half of the pathway. The enzyme activities in stimulated cells, cultured for 72 h, were similar to the activities measured in long-term lymphoid lines. Starch-gel electrophoresis was used to examine the isozyme patterns of the enzymes before and after exposure of the lymphocytes to PHA. Six of the enzymes showed isozyme patterns unchanged by stimulation. Four of the enzymes, aldolase, triosephosphate isomerase, enolase and lactate dehydrogenase, showed different isozyme patterns in stimulated cells from those seen in uncultured or unstimulated cells. The electrophoretic results showed a good correlation in isozyme pattern between uncultured lymphocytes and cultured unstimulated lymphocytes, and between PHA-stimulated lymphocytes and long-term lymphoid lines.

Cells, Cultured↗
PubMed1980

Assignment of the human locus determining phosphoglycolate phosphatase (PGP) to chromosome 16.

The segregation of human phosphoglycolate phosphatase has been studied in 52 independent human-rodent hybrids and 69 subclones. The results suggest that human PGP is on chromosome 16. Family data suggest that PGP is not close to 16qh or alpha Hp. The most likely regional assignment for PGP would appear to be 16p13 or 16p12, but a site on 16q cannot be entirely excluded. New data on 16qh and alpha Hp suggest that the male recombination fraction between these loci is about 0.2.

Alleles↗
PubMed1980

Genetical and biochemical studies on human phosphoserine phosphatase.

1. Phosphoserine phosphatase (PSP), specific for D- and L-phosphoserine, has been identified in all human tissues. 2. PSP shows no activity towards phosphorylated serine residues in phosphoproteins. 3. In most tissues, PSP consists of a single major isozyme, probably determined by a single autosomal locus. 4. Other isozymes, identified quite frequently in such post-mortem tissues as kidney and liver, appear to be due to post-translational modification, the mode of which has not yet been identified. 5. Two different rare electrophoretic variants have been identified in 1% and 0.25% of 378 post-mortem kidneys (PSP 2-1 and PSP 3-1 respectively). 6. The three banded isozyme pattern of the rare variants suggests PSP is a dimeric enzyme. From gel filtration results the subunit molecular size is 26 000 daltons. 7. Homologous PSP isozymes have been detected in primates with similar electrophoretic mobility to that of the human enzyme.

Alleles↗
PubMed1980

Biochemical genetics of the pentose phosphate cycle: human ribose 5-phosphate isomerase (RPI) and ribulose 5-phosphate 3-epimerase (RPE).

1. Staining procedures are described for the detection after starch-gel electrophoresis of ribose-5-phosphate isomerase (RPI) and ribulose 5-phosphate 3-epimerase (RPE). 2. Both RPI and RPE were detected in all human tissues including red cells, lymphocytes and fibroblasts. 3. No evidence was found for more than one structural gene locus for either enzyme. 4. No allelic variants of either enzyme were found in erythrocyte lysates from over 200 unrelated individuals. 5. Preliminary data are presented which suggest that differences in tissue RPE isozyme patterns may be due to endogenous proteolytic activity. 6. Electrophoretic analysis of RPE and RPI isozyme patterns in extracts of man/mouse hybrid cells indicates that RPE is probably a dimer and RPI may also be polymeric.

Animals↗
PubMed1979

Characterization of human carbonic anhydrase III from skeletal muscle.

A third form of human carbonic anhydrase (CA III), found at high concentrations in skeletal muscle, has been purified and characterized. This isozyme shows relatively poor hydratase and esterase activities compared to the red cell isozymes, CA I and CA II, but is similar to these isozymes in subunit structure (monomer) and molecular size (28,000). CA III is liable to posttranslational modification by thiol group interaction. Monomeric secondary isozymes, sensitive to beta-mercaptoethanol, are found in both crude and purified material and can be generated in vitro by the addition of thiol reagents. Active dimeric isozymes, generated apparently by the formation of intermolecular disulfide bridges, also occur but account for only a small proportion of the total protein and appear only when the concentration of CA III is particularly high.

Adult↗
PubMed1979

A comparison of the biochemical properties of the human diaphorase (DIA3) isozymes determined by the common alleles DIA13, DIA23 and DIA33.

(1) Various buffer systems for the starch gel electrophoresis of human diaphorase isozymes have been explored. Electrophoresis in a Tris/Borate system at pH 8.6 which includes 70 micron NADH in the gel and cathodal electrode buffers, provides good resolution of the six DIA3 phenotypes previously resolved by isoelectric focusing. (2) The variant genes DIA13, DIA23 and DIA33 occur with frequencies of about 0.76, 0.23 and 0.01 respectively in the English population. (3) The isozymes determined by the least common gene, DIA33, are markedly different from the isozymes determined by DIA13 and DIA23 in their relatively low heat stability, high affinity for Blue Sepharose and slow anodal electrophoretic mobility in buffer systems containing borate. The DIA3 1 and DIA3 2 isozymes are similar to one another in these characteristics.

Alleles↗
PubMed1979

The genetic determination of fumarase isozymes in human tissues.

(1) A method for the starch gel electrophoresis of human fumarase has been devised which resolves two groups of isozymes: one group (FHM) is associated with the mitochondria, the other (FHS) is cytosolic. (2) Tissue to tissue variation in the complexity of the isozyme patterns and the examination of red cells fractionated according to their age by density gradient centrifugation suggest that the least anodal isozymes of the FHS group and ofthe FHM group are modified in vivo with the generation of several secondary isozymes. (3) Red cells, which display only FHS isozymes, were screened from 776 European and 100 Nigerian individuals and a single electrophoretic variant (phenotype FH 2-1) was identified in a middle-aged male from England. The same variant was identified in a paternal aunt and the data suggest that the variant repressents heterozygosity for the common (FH1) allele and a rare variant (FH2) allele at an autosomal locus. (4) Fibroblasts and white cells from the FH 2-1 individual showed variation in the FHM and FHS isozymes indicating that the mitochondrial and the soluble forms of fumarase are determined at the same structural locus.

Centrifugation, Density Gradient↗
PubMed1979

Red cell adenosine deaminase (ADA) polymorphism in Southern Africa, with special reference to ADA deficiency among the !Kung.

Studies have been carried out on polymorphism of adenosine deaminase in 36 Southern African populations comprising more than 3000 individuals. The common variant allele ADA2 has been found to attain polymorphic frequencies only in those populations descended from non-indigenous (i.e. non-Negro and non-Khoisan) groups. Its presence in certain other populations at low frequencies could be ascribed to small-scale Caucasoid admixture. A deficiency of the enzyme is found in certain members of the !Kung division of the San ('Bushman'). The low levels of enzyme activity are not associated with severe combined immunodeficiency and the gene which determines them appears to be polymorphic in the !Kung and possibly in some other San populations as well as possibly in Negro populations which have received substantial contributions of San genes.

Adenosine Deaminase↗
PubMed1979

Further characterization of the human fumarase variant, FH 2--1.

1. Further investigation of fumarase using lymphoblastoid cells derived from an individual of the FH 2--1 phenotype has confirmed that the mitochondrial (FHM) and soluble (FHS) forms of fumarase are determined at the same structural locus. 2. The FH 2--1 variant is associated with enzyme deficiency: c. 70% of normal in lymphoblastoid cells and c. 20% of normal in red cells. 3. The pH optimum and apparent Michaelis constant of the variant fumarase were normal but heat-inactivation studies suggest that the isozymes containing polypeptides determined by the variant allele are unstable.

Cell Line↗
PubMed1979

Affinity electrophoresis of human alcohol dehydrogenase (ADH) isozymes.

1. The effects of coenzyme NAD and related compounds on the electrophoretic properties of the human ADH isozymes have been examined by the technique of affinity electrophoresis. 2. Incorporation of NAD, NADH or AMP into a starch-gel matrix leads to retardation in the cathodal mobilities of the gamma 2 gamma 2 and alpha alpha isozymes, but not the beta 1 beta 1 and gamma 1 gamma 1 isozymes. The heterodimeric isozymes show intermediate effects, and the genetic polymorphism at the ADH3 locus is only discernible if electrophoresis is carried out in the presence of coenzyme. 3. The behaviour of the ioszymes can be attributed to slight differences between the products (alpha, beta 1 and gamma 1) of the common alleles at the three ADH loci and a pronounced difference between the products (gamma 1 and gamma 2) of the alternative alleles at the ADH3 locus in their affinities for the cofactor NAD.

Adenosine Monophosphate↗
PubMed1979

Congenital haemolytic anaemia resulting from glucose phosphate isomerase deficiency: genetics, clinical picture, and prenatal diagnosis.

Glucose phosphate isomerase (GPI) deficiency with severe haemolysis and hydrops fetalis was found in the first child of unrelated, healthy Caucasian parents. The child died at 3 hours. Both parents were found to have 50% of normal red cell GPI activity and qualitative tests on their red cells and white cells showed that each was heterozygous for a different GPI variant allele associated with enzyme deficiency. Tests on the placenta showed that the propositus was a 'compound' heterozygote. Examination of amniotic cells obtained by amniocentesis on the mother at 28 weeks in her second pregnancy led to the prenatal diagnosis of GPI deficiency. This second child, a 'compound' heterozygote at the GPI locus indistinguishable from the first, was successfully treated by immediate exchange transfusion and subsequent blood transfusions.

Adult↗
PubMed1978

Genetic polymorphism of human phosphoglycolate phosphatase (PGP).

1. A method has been devised for the detection after starch-gel electrophoresis of phosphoglycolate phosphatase (PGP) isozymes. 2. PGP isozymes can be detected in all human tissues including red cells, lymphocytes and cultured fibroblasts. The highest activities occur in skeletal muscle and cardiac muscle. 3. PGP is a relatively specific phosphatase which shows enhanced activity in the presence of mercaptoethanol at a neutral pH.4. Six different commonly occurring electrophoretic types of PGP have been identified. Family studies indicate that they are determined by three alleles at an autosomal locus (PGP). 5. The gene frequencies of PGP1, PGP2 and PGP3 in a random sample of Europeans were 0.826, 0.129 and 0.045 respectively. 6. The three-banded isozyme patterns seen in heterozygotes suggest that PGP is a dimeric enzyme.

Electrophoresis, Starch Gel↗
PubMed1978

Blue Sepharose chromatography of human alcohol dehydrogenase: evidence for interlocus and interallelic differences in affinity characteristics.

1. The various isozymes of human alcohol dehydrogenase have been examined by Blue Sepharose column chromatography. 2. The products (alpha, beta1 and gamma1) of the common alleles at the three ADH loci (ADH1 ADH2 and ADH3 respectively) were found to show slight, but significant differences in their affinities for Blue Sepharose. The order of affinity of the homodimeric isozymes was: alphaalpha less than gamma1gamma1 less than beta1beta1. The heterodimeric isozymes showed intermediate affinities. 3. The products (gamma1 and gamma2) of the common alleles (ADH31 and ADH32 respectively) at the ADH3 locus showed a pronounced difference in their affinities: the gamma1gamma1 isozyme was firmly adsorbed by Blue Sepharose, whereas the gamma2gamma2 isozyme was not adsorbed. The heterodimeric gamma1gamma2 isozyme was intermediate in its behaviour. 4. The 'usual' and 'atypical' forms of ADH were indistinguishable by Blue Sepharose column chromatography. 6. The 'anodal' form of ADH showed no affinity for Blue Sepharose.

Adult↗