Rl. Zheng et Rg. Kemp, PHOSPHOFRUCTO-1-KINASE - ROLE OF CHARGE NEUTRALIZATION IN THE ACTIVE-SITE, Biochemical and biophysical research communications, 214(3), 1995, pp. 765-770
Previous studies of Escherichia coli phosphofructo-1-kinase have shown
that mutation of Asp 127 lowers kcat by 5 orders of magnitude. As sho
wn here, introduction of a second mutation (R252Q) that neutralizes a
positive charge in the active site increases activity of D127S by 100
fold, suggesting that part of the effect of the Asp mutation may be at
tributed to non-specific charge interactions. This conclusion is suppo
rted by the fact that the R252Q mutant shows a pH dependence that is t
he reverse of the wild type enzyme, whereas the double mutant has a pH
dependence that resembles that of wild type enzyme, although somewhat
attenuated. (C) 1995 Academic Press, Inc.