The effect of storage on the kinetic properties of sheep hepatic pyruvate kinase.
Biochem Med Metab Biol
; 35(1): 50-8, 1986 Feb.
Article
em En
| MEDLINE
| ID: mdl-3778676
ABSTRACT
The kinetic properties of purified sheep hepatic pyruvate kinase change upon storage. Assayed at 0.5 mM fructose-1,6-diphosphate and 2 mM ADP, saturation of fresh enzyme with phosphoenolpyruvate is hyperbolic, with KPEP = 0.1 mM (pH 7.5, and 30 degrees C). Under similar conditions enzyme stored at -20 degrees C for 1 week or more yields a nonlinear Lineweaver-Burk plot for PEP. The data may be accounted for by the appearance of two enzymic forms with identical turnover numbers, but different KPEP (0.035 +/- 0.005 and 12.4 +/- 0.6 mM). Storage also increases the concentration of fructose-1,6-diphosphate required for maximal activation from nanomolar to millimolar levels. Assayed at 2 mM ADP and 2 mM PEP, the apparent KFDP is 10 mM. Preincubation of stored enzyme with PEP in the presence of mercaptoethanol leads to significant reversion to original kinetic properties. Available data suggest that the storage-dependent change in kinetic behavior rises from changes in subunit conformation and not from dissociation into subunits.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Piruvato Quinase
/
Fígado
Limite:
Animals
Idioma:
En
Ano de publicação:
1986
Tipo de documento:
Article