الفهرس 
Malate dehydrogenaseOnly 14 pages are availabe for public view
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Abstract
Cryptococcus neofomuzns is a basidiomycetious yeast that is an opportunistic pathogen of AIDS patients. Current therapeutic approaches to cryptococcal meningitis involve drugs that interact with the ergosterol component of the plasma membrane or that inhibit ergosterol biosynthesis. Fatty acid synthetase complex (FAS) has been purified and characterized from C. neofomuzns with the long range goal of developing new therapeutic approaches directed toward the phospholipid component of the plasma membrane. C. neofom2cms is the first basidiomycete and the first pathogenic yeast from which the fatty acid synthetase complex has been purified. C. neoformans FAS is a multifunctional enzyme composed of two nonidentical subunits of molecular masses 210 kDa and 180 kDa. Properties of the purified enzyme include: Vmax=3.5 unitslmg; Km acetyl-CoA= 19 pM; Km malonyl-CoA=5 pM; Km NADPH =6 pM and the optimum pH is 7.5. The purified enzyme was sensitive to the change of the assay buffer ionic strength with optimal activity at 100 rnM KC1. Product inhibition patterns were consistent with the proposed kinetic mechanism for the yeast enzyme (Ping Pong): NADP was competitive vs. NADPH, uncompetitive vs. acetyl-CoA and malonyl-CoA; CoA was competitive vs. acetyl- CoA and malonyl-CoA , uncompetitive vs. NADPH; palmitoyl-CoA was competitive vs. malonyl- CoA, noncompetitive vs.acety1-CoA and NADPH. The purified enzyme was inhibited reversibly by zinc ion and the inhibition was noncompetitive with respect to the substrates (acetyl-CoA, malonyl-CoA and NADPH). C. neofomns FAS was inhibited irreversibly by cerulenin with second order rate constant 0.46 mh4-lsec-l. The purified enzyme was inhibited by high molecular weight fractions of heparin and dextran sulfate (polyanionic polymers).