Activities | Families | Sequences | Fold types | References | Help
B6db references: 83238337

type Journal Article
authors Nakamura, Y.; Tolbert, N. E.
title Serine: glyoxylate, alanine:glyoxylate, and glutamate:glyoxylate aminotransferase reactions in peroxisomes from spinach leaves
journal J Biol Chem
ui 83238337
year (1983)
volume 258
number 12
pages 7631-8.
keywords Alanine Transaminase/isolation & purification/*metabolism
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:glyoxylate aminotransferase activity has not been incorporated into schemes for the oxidative photosynthetic carbon cycle.
last changed 2002/11/12 16:17

B6db references