PHOSPHOENOLPYRUVATE CARBOXYLASE - ALTERATION OF CATALYTIC AND REGULATORY PROPERTIES BY SITE-DIRECTED MUTAGENESIS AND ISOLATION OF THE GENE FROM AN EXTREME THERMOPHILE
K. Izui et al., PHOSPHOENOLPYRUVATE CARBOXYLASE - ALTERATION OF CATALYTIC AND REGULATORY PROPERTIES BY SITE-DIRECTED MUTAGENESIS AND ISOLATION OF THE GENE FROM AN EXTREME THERMOPHILE, Energy conversion and management, 36(6-9), 1995, pp. 751-754
Citations number
NO
Categorie Soggetti
Energy & Fuels",Mechanics,"Physics, Nuclear",Thermodynamics
The roles of several conserved amino acid residues in phosphoenolpyruv
ate carboxylase (PEPC, EC4.1.1.31) of E.coli were studied by site-dire
cted mutagenesis. Mutant enzymes H138N (His138 replaced by Asn) and R5
87S lost the original catalytic activity but revealed the weak activit
y of HCO3- -dependent hydrolysis of PEP to yield pyruvate. By the use
of H138N the formation of carboxyphosphate, a postulated reaction inte
rmediate, was demonstrated for the first time. K620S and R438C were al
most insensitive to an allosteric feedback inhibitor, aspartate, and t
he latter showed a tendency to dissociate to dimer. Furthermore, the g
ene for extremely thermostable PEPC was cloned and expressed in E. col
i.