Physico-chemical properties of guinea pig liver argininosuccinate synthetase

Abstract

The behaviour of guinea pig liver argininosuccinate synthetase with respect to pH, temperature and kinetic parameters of substrates and inhibitors has been investigated.The enzyme shows the maximum activity at pH 8 and maximum stability (15 min at 30 degrees C) at pH in the range of 6.5 and 8.With respect to temperature it remains stable (15 min at pH 8) up to 40 degrees C.The results found for the Km values of the enzyme substrates L-citrulline, L-aspartate and ATP are 0.038 mM, 0.045 mM and 0.090 mM respectively.L-ornithine, diaminopimelic acid, pyrophosphate and ATP acted as inhibitors of the enzyme (competitive or not, according to the case).These kinetic studies of substrates and inhibitors were carried out with a partially purified fraction of the enzyme which had been purified 7.3 fold, which practically suppressed the ATP-ase activity, present in crude extracts.