Inactivation of XXXX mutase and @entity908 kinase isoenzymes in human serum.

@entity1 @entity908 @entity16055 @entity3902 @entity95 @entity1432 @entity460 @entity583 @entity1098 @entity46789
AIMS/BACKGROUND: Total @entity16055 mutase (PGM) activity in serum has been shown to be increased in acute @entity583 with the same time course as @entity908 kinase (CK) activity. However, the increase in the muscle (MM) and in the cardiac (MB) PGM isoenzymes was not as high as expected. The present study was undertaken to characterise PGM inactivation by serum and to compare it with serum CK inactivation. METHODS: The PGM and the CK activities of extracts of @entity1 heart, skeletal muscle, and brain were determined spectrophotometrically after incubation with different media, namely: plasma, whole serum, dialysed serum, heated serum, serum ultrafiltrate, urate solution, and buffer solution. RESULTS: Type MM PGM was inactivated by plasma, whole serum, heated serum, dialysed serum, and serum ultrafiltrate. Inactivation in dialysed serum was reduced by @entity1098 and largely reversed by @entity1432 agents. Inactivation in serum ultrafiltrate was not prevented by @entity1098 and only partially reversed by @entity3902 . The muscle and type BB CK isoenzymes were inactivated in all the tested media. The incubation of @entity1 and @entity95 skeletal muscle PGM and CK in urate solution showed that urate does not affect mutase activity under conditions that inactivate CK. CONCLUSIONS: These results confirm the mechanisms of CK inactivation proposed by others and show that the type M @entity46789 subunit is inactivated by two different mechanisms, which appear to involve the thiol groups of the enzyme. One mechanism is caused by either a protein component or a protein bound serum component and involves @entity460 ions and/or another chelatable metal ion. The other mechanism is caused by a lower molecular weight serum component and is metal ion independent.
