J. Biol. Chem., Vol. 261, Issue 24, 11049-11055, 08, 1986
Amino acid sequence of the pyruvate and the glyoxylate active-site lysine peptide of Escherichia coli 2-keto-4-hydroxyglutarate aldolase
CJ Vlahos and EE Dekker
Pure 2-keto-4-hydroxyglutarate aldolase of Escherichia coli, a "lysine-
type" trimeric enzyme which has the unique properties of forming an
"abortive" Schiff-base intermediate with glyoxylate (the aldehydic
product/substrate) and of showing strong beta-decarboxylase activity toward
oxalacetate, binds any one of its substrates (2-keto-4- hydroxyglutarate,
pyruvate, or glyoxylate) in a competitive manner. To determine whether the
substrates bind at the same or different (juxta- positioned) sites and what
degree of homology might exist between the active-site lysine peptide of
this enzyme and that of other lysine-type (Class I) aldolases or
beta-decarboxylases, the azomethine formed separately by this aldolase with
either [14C]pyruvate or [14C]glyoxylate was reduced with CNBH3-. After each
enzyme adduct was digested with trypsin, the 14C-labeled peptide was
isolated, purified, and subjected to amino acid analysis and sequence
determination. In each case, the same 14-amino acid lysine-peptide was
isolated and found to have the following primary sequence:
Glu-Phe-*Lys-Phe-Phe-Pro-Ala- Glu-Ala-Asn-Gly-Gly-Val-Lys (where * = the
active-site lysine). Hence, glyoxylate competes for, and inhibits aldolase
activity by reacting with, the one active-site lysine residue/subunit. This
active-site lysine peptide has a high degree (65%) of homology with that of
2-keto- 3-deoxy-6-phosphogluconate aldolase of Pseudomonas putida but is
not similar to that of any Class I fructose-1,6-bisphosphate aldolase or of
acetoacetate beta-decarboxylase of Clostridium acetobutylicum. Furthermore,
it was found that extensive reaction of glyoxylate with the N-terminal
amino group of this enzyme may well be general complicating factor in
sequence studies with proteins plus glyoxylate.