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W R Osborne

Publications and source records attributed to W R Osborne.

62 records · Page 4Linked to original sources
PubMed1978

Use of the integrated steady state rate equation to investigate product inhibition of human red cell adenosine deaminase and its relevance to immune dysfunction.

The analysis of progress curves using the integrated rate equation was applied to the adenosine deaminase-catalyzed conversion of adenosine to inosine. Adenosine deaminase was purified from human red blood cells of phenotypes ADA 1, ADA 2, and ADA 2-1. For all three types, no measurable product inhibition by inosine was observed. These results do not confirm the hypothesis that inosine accumulation in purine nucleoside phosphorylase deficiency causes adenosine deaminase inhibition, resulting in a common mechanism for the immune defects related to these two enzyme deficiencies.

Adenosine Deaminase↗
PubMed1977

Purine nucleoside phosphorylase deficiency. Evidence for molecular heterogeneity in two families with enzyme-deficient members.

Purine-nucleoside phosphorylase (NP) deficiency is associated with severely defective thymus-derived (T)-cell and normally functioning bone marrow-derived (B)-cell immunity. In this study, two unrelated families with a total of three NP deficient members were investigated. High pressure liquid chromatography of the plasma of the three patients showed inosine levels greater than 66 muM. This nucleoside was absent from the plasma of their parents and control samples.NP was purified from normal human erythrocytes by affinity chromatography and an antiserum prepared in rabbits was used to study the NP variants in the two families. In family M the patient had no detectable erythrocyte NP activity and no detectable immunological-reacting material (irm) to the NP antibody. The parents, who are second cousins, had less than one-half of normal enzyme activity and approximately 14% irm attributable to a variant protein. Their electrophoretic patterns revealed a series of isozymes with slower than normal migration. In family B the patients had 0.5% residual enzyme activity and about one-half normal irm. Their electrophoretic pattern showed faintly staining bands which migrated faster than normal NP. The mother of the patients had one-half normal enzyme activity, 11% irm attributable to her variant protein, and a normal electrophoretic pattern. The father had less than one-half normal enzyme activity, equal amounts of normal and variant irm, and an electrophoretic pattern that showed increased activity of the more rapidly migrating isozyme bands.The combined use of immunological and electrophoretic techniques has shown the presence of three separate mutations; one in family M and two in family B associated with severely defective T-cell function.

Adult↗
PubMed1976

Biochemical characterization of the human carbonic anhydrase variant CA Ih Hiroshima.

Some biochemical properties of a new red cell human carbonic anhydrase variant, CA Ih Hiroshima, have been determined. Evidence is presented that the amino acid substitution in the Japanese variant is not the same as the previously characterized CA Ic variant from Guam of similar electrophoretic mobility. Based on a comparison with the normal CA I isoenzyme, a proposal for the site of the amino acid substitution is presented.

Amino Acid Sequence↗
PubMed1974

Thermal inactivation studies of normal and variant human erythrocyte carbonic anhydrases by using a sulphonamide-binding assay.

Heat-inactivation studies were carried out on the two primary erythrocyte carbonic anhydrase isoenzymes, CA I and CA II, and the secondary isoenzyme of CA I, CA I (+1). In addition, two genetic variants of human isoenzyme CA I, CA Id Michigan (100 Thr-->Lys) and CA If London (102 Glu-->Lys), and one variant of isoenzyme CA II, CA IIh (251 Asn-->Asp), were similarly analysed. The first-order rate constants and Arrhenius plots for these six enzyme forms showed that (1) isoenzyme CA II is more heat-stable than CA I, (2) isoenzyme CA I (+1) is less heat-stable than CA I, (3) the variants CA IIh and CA If London are less heat-stable than the normal enzymes, and (4) isoenzyme CA Id Michigan is more heat-stable than normal CA I. From the values of the slopes of the Arrhenius plots, the energy of activation (E(a)) for each isoenzyme and isoenzyme variant was determined, and the following thermodynamic activation parameters were calculated at 55 degrees C: the free energy of activation (DeltaG(double dagger)), the activation enthalpy (DeltaH(double dagger)) and the activation entropy (DeltaS(double dagger)). The DeltaG(double dagger) for the enzymes shows a relative constancy with compensating variation in DeltaH(double dagger) and DeltaS(double dagger). When the values for DeltaH(double dagger) are plotted against DeltaS(double dagger), an increase in DeltaH(double dagger) involves a concomitant increase in DeltaS(double dagger).

Azo Compounds↗
PubMed1973

Partial purification and properties of the common inherited forms of adenosine deaminase from human erythrocytes.

1. The partial purification of adenosine deaminase, types 1, 2 and 2-1, from human erythrocytes is described. 2. The isoenzyme components characteristic of the three forms of the enzyme were partially resolved by chromatography on DEAE-Sephadex. 3. Gel chromatography of the various forms of the enzyme gave estimates of the molecular weights in the range 30000-35000. 4. Electrophoresis in starch gels containing increasing percentages of starch did not reveal any differences in molecular weight between the genetic variants or their isoenzyme components. 5. Analytical isoelectric-focusing experiments in polyacrylamide gels gave the following pI values for the four isoenzyme components present in type 2-1 erythrocytes: 4.70, 4.83, 4.94 and 5.06. 6. All forms of the enzyme gave K(m) values for adenosine of about 30mum and K(i) values of about 8mum for the competitive inhibitor purine riboside. 7. Reaction rates of the type 1 and 2 enzymes were measured at different temperatures. Both enzymes gave values for the energy of activation for hydrolysis of adenosine of about 33.4kJ/mol (8kcal/mol). 8. Heat inactivation of all forms of the enzyme was markedly dependent on ionic strength, the rate of inactivation increasing with increasing ionic strength. The type 1 and type 2 forms of the enzyme differed significantly in their susceptibility to heat inactivation. From the variation of rates of inactivation with temperature, values were obtained for the energies of activation for the heat inactivation of both enzymes as follows: type 1 enzyme 275.5kJ/mol (65.9kcal/mol) and type 2 enzyme 241.6kJ/mol (57.8kcal/mol.).

Adenosine↗