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T J Mantle

Publications and source records attributed to T J Mantle.

At least 55 records · Page 3Linked to original sources
PubMed1984

Evidence for two forms of ligandin (YaYa dimers of glutathione S-transferase) in rat liver and kidney.

CM-cellulose chromatography of rat liver and kidney cytosol at pH6 reveals the presence of a second Ya-subunit dimer of glutathione S-transferase (GST-F) in addition to the recently described GST-YaYa (GST-L; our nomenclature) [Hayes & Clarkson (1982) Biochem. J. 207, 459-470]. The two forms are structurally similar (by the criteria of CNBr- and Staphylococcus-V8-proteinase-cleavage peptide maps), and both are sensitive to inhibition by haemin. However, their kinetic parameters with 1-chloro-2,4-dinitrobenzene are quite distinct, and they show differential inducibility by phenobarbitone. These results suggest a similar heterogeneity in Ya-subunits to that previously described for Yb-subunits of glutathione S-transferase and indicate that significant gene duplication may have occurred in these multifunctional intracellular binding proteins.

Animals↗
PubMed1983

The effect of pH on the kinetics of arylsulphatases A and B.

The effect of pH on the kinetics of rat liver arylsulphatases A and B is very similar and shows that two groups with pK values of 4.4-4.5 and 5.7-5.8 are important for enzyme activity. Substrate binding has no effect on the group with a pK of 4.4-4.5; however, the pK of the second group is shifted to 7.1-7.5 in the enzyme-substrate complex. An analysis of the effect of pH on the Ki for sulphate inhibition suggests that HSO4-is the true product. A model is proposed that involves the two ionizing groups identified in the present study in a concerted general acid-base-catalysed mechanism.

Cerebroside-Sulfatase↗
PubMed1982

The nature of the inhibition of rat liver monoamine oxidase types A and B by the acetylenic inhibitors clorgyline, l-deprenyl and pargyline.

The kinetics of inhibition of rat liver mitochondrial monoamine oxidase by clorgyline, l-deprenyl and pargyline are consistent with a mechanism whereby a reversible interaction between the inhibitor and the enzyme active site under conditions of thermodynamic equilibrium is followed by a time-dependent formation of the covalently-bound enzyme-inhibitor adduct. The Ki value for the reversible interaction between clorgyline and monoamine oxidase A is about 1000 times lower than that towards the B-form of the enzyme, and this difference is sufficient to account for most, but not all, of the selectivity of the inhibition caused by this compound. The Ki value of the monoamine oxidase B selective inhibitor l-deprenyl towards that form of the enzyme is only about 40-fold lower than that towards the A-form. However, in this case, the rate of formation of the irreversible adduct is considerably faster for the B-form than for the A-form and this makes a major contribution to the selectivity of this compound. Pargyline shows a Ki value towards monoamine oxidase B that is only 8 times lower than that towards the A-form and in this case the rates of formation of the enzyme-inhibitor adducts are similar. The significance of these results are discussed in terms of the selective inhibition of monoamine oxidase.

Animals↗
PubMed1982

Purification and characterization of the multiple forms of aldehyde reductase in ox kidney.

Aldehyde reductase from ox kidney cytosol has been fractionated into four forms, two of which have been purified to apparent homogeneity. One of the minor forms is shown to be heterogenous on polyacrylamide-gel electrophoresis. The substrate specificities of the four forms using a variety of aldehydes and ketones are presented. The sensitivity of the various forms to inhibition by sodium valproate, sodium barbitone and various benzodiazepines has been determined. The relationship of these forms to the previously described hexonate dehydrogenase, aldose reductase and prostaglandin dehydrogenase is discussed.

Alcohol Oxidoreductases↗
PubMed1982

The kinetic mechanism of the major form of ox kidney aldehyde reductase with D-glucuronic acid.

The steady-state kinetics of the major form of ox kidney aldehyde reductase with d-glucuronic acid have been determined at pH7. Initial rate and product inhibition studies performed in both directions are consistent with a Di-Iso Ordered Bi Bi mechanism. The mechanism of inhibition by sodium valproate and benzoic acid is shown to involve flux through an alternative pathway.

Alcohol Oxidoreductases↗
PubMed1982

The slow kinetic transients of arylsulphatase A.

A simple model is described to account for the anomalous time course of arylsulphatase A. In the case of the ox liver and human placental enzymes the enzyme-nitrocatechol sulphate complex can, in addition to forming products, slowly break down to form an inactive species which can turn in slowly regenerate active enzyme. When the inactive form binds sulphate the rate of reactivation is enhanced, 218-fold in the case of the ox enzyme. Rat liver arylsulphatase A is refractory to reactivation by sulphate.

Animals↗