PMID: 6408081Jun 25, 1983

Serine: glyoxylate, alanine:glyoxylate, and glutamate:glyoxylate aminotransferase reactions in peroxisomes from spinach leaves

The Journal of Biological Chemistry
Y Nakamura, N E Tolbert

Abstract

Two different aminotransferases, that have glyoxylate as the amino acceptor, have specific activities of 1 to 2 mumol . min-1 . mg of protein-1 in the isolated peroxisomal fraction from spinach leaves. Their properties were evaluated after separation on a hydroxylapatite column. Both enzymes had a Km for glyoxylate of 0.15 mM and an amino acid Km of 2 to 3 mM. Reactions proceeded by a Ping Pong Bi Bi mechanism. Serine:glyoxylate aminotransferase was relatively specific for both substrates and could only be slightly reversed with 100 mM glycine, although the Ki of glycine was 33 mM. The glutamate:glyoxylate amino-transferase protein was equally active in catalyzing an alanine:glyoxylate aminotransferase reaction, but the reverse reactions with 100 mM glycine were hardly measureable, although the Ki (glycine) was 8.7 mM. Protection against hydroxylamine inhibition from reaction with pyridoxal phosphate was used to investigate the specificity of amino acid binding. Substrate amino acids protected at about the same concentration as their Km, while glycine protected at its Ki concentration. Thus, the nearly irreversible catalysis with glycine is not due to a failure to bind glycine. The significance of a peroxisomal alanine:glyoxyla...Continue Reading

Related Concepts

Spinach preparation
Enzymes, antithrombotic
Amino Acids, I.V. solution additive
Spinacia oleracea
Serine-glyoxylate aminotransferase
Pyridoxal Phosphate
Peroxisomal
Glycine
Glycine (Plant)
Glyoxylates

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