The selenite-induced glutathione peroxidase in Chlamydomonas reinhardtii has been purified about 323-fold with a 10% yield, as judged by PAGE. The native enzyme had an Mr of 67,000 and was composed of four identical subunits of Mr 17,000. Glutathione was the only electron donor, giving a specific activity of 193.6 mumol/min per mg of protein. L-Ascorbate, NADH, NADPH, pyrogallol, guaiacol and o-dianisidine did not donate electrons to the enzyme. In addition to H2O2, organic hydroperoxides were reduced by the enzyme. The Km values for glutathione and H2O2 were 3.7 mM and 0.24 mM respectively. The enzyme reaction proceeded by a Ping Pong Bi Bi mechanism. Cyanide and azide had no effect on the activity. The enzyme contained approx. 3.5 atoms of selenium per mol of protein. On immunoprecipitation, Chlamydomonas glutathione peroxidase was precipitated and its activity was inhibited about 90% by the antibody raised against bovine erythrocyte glutathione peroxidase. The antibody also cross-reacted with the subunits of Chlamydomonas glutathione peroxidase in Western blotting SDS/PAGE. In terms of enzymic, physico-chemical and immunological properties, the experimental results demonstrate clearly that Chlamydomonas glutathione peroxidase resembles other well-characterized glutathione peroxidases from animal sources that contain selenium.

The effect of tricarboxylic acid-cycle intermediates and related compounds on 2-oxoglutarate decarboxylase activity was investigated. The addition of L-glutamate to Euglena cells grown on glucose/(NH4)2SO4 medium resulted in an increase in 2-oxoglutarate decarboxylase activity, which was abolished by the simultaneous addition of cycloheximide. Immunochemical titration, immunoblot analysis and labelling in vivo with antibody raised against 2-oxoglutarate decarboxylase showed that the increase in 2-oxoglutarate decarboxylase activity was due to synthesis of new protein and not to activation of pre-existing protein. The experimental results reported here demonstrate that L-glutamate is assimilated by the pathway, via 2-oxoglutarate, that consists of L-glutamate-oxaloacetate aminotransferase, 2-oxoglutarate decarboxylase and succinate semialdehyde dehydrogenase, rather than by the gamma-aminobutyrate shunt, consisting of L-glutamate decarboxylase and gamma-aminobutyrate aminotransferase.

The chemical modification of lipase with the hydrophobic group such as Z (benzyloxycarbonyl) or Z(NO2) (p-nitro-Z) is found to bring about a marked improvement of the enantioselectivity in isopropyl ether and an inversion of the solvent effects on the enantioselectivity.

No abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.