Temperature perturbation of aqueous buffered oxaloacetate solutions

Abstract

The 215 and 260 mμ absorbance patterns of oxaloacetic acid (OAA) solutions at various pH values, subjected to temperature shifts, show a progression in both the maximum absorbance reached and the nature of the temperature effect. The levels of pyruvate, the product of OAA decarboxylation, change appreciably as well. A multiple equilibrium system is proposed to relate OAA acid dissociations, keto–enol tautomerization, and decarboxylation.

Studying enzymes by in vivo 13C magnetic resonance spectroscopy

“…In the brain, the other transamination reactions that use oxaloacetate as an amino group acceptor are not distinguishable from the AAT reaction in magnetization transfer between oxaloacetate and aspartate. Because the dominant keto form of oxaloacetate [104, 105] acts as the substrate for MDH and AAT [104, 106], the chemical exchange between the keto form of oxaloacetate with its minor enol and gem-diol forms causes no significant leakage of perturbed magnetization.…”

Identification of the high‐molecular‐mass mitochondrial oxaloacetate keto‐enol tautomerase as inactive aconitase

“…Subsequently, two highly purified proteins, with apparent molecular masses of 37 and 80 kDa, capable of the oxaloacetate ketoenol tautomerase activity were isolated from bovine heart mitochondrial matrix [7]. Both mitochondrial enzymes were found to be quite different from that previously obtained from porcine kidney extracts [5,8]. We have pointed out that the proteins described may either be the unique mitochondrial oxaloacetate keto-enol tautomerases, or their tautomerase activity is the partial reaction of certain enzymes capable of oxaloacetate binding [7].…”

“…Although no metabolic sources of the enolisomer have so far been found, the specific enzyme named oxaloacetate keto-enol tautomerase (EC 5.3.2.2) has been found and partially purified from porcine kidney extracts [5]. Recently we have described the malate dehydrogenase activity of succinate dehydrogenase (EC 1.3.99.1), and the enolisomer of oxaloacetate has been identified as the reaction product [6].…”