Abstract
A new strategy of potentially broad application for probing transition-state (TS) analogy in enzymatic systems is described in this paper. The degree to which a series of phosphonate inhibitors act as TS analogues of rat carboxypeptidase A1 has been determined for the wild-type enzyme, for the R127K, R127M, and R127A mutants, and for the R127A mutant in the presence of 0.5 M guanidine hydrochloride. The impact that the mutations have on the inverse second-order rate constants (Km/kcat) for substrate hydrolysis is mirrored by the effect on the inhibition constants (Ki) for the corresponding phosphonate inhibitors. These results demonstrate that the phosphonate moiety mimics some of the electronic as well as the geometric characteristics of the TS. A similar but distinctly separate correlation is observed for tripeptide analogues in comparison to analogues of the dipeptide Cbz-Gly-Phe, reflecting an anomalous mode of binding for the latter system. The selective rate increases and corresponding enhancement in inhibitor binding observed on addition of 0.5 M guanidine hydrochloride to the R127A mutant indicate that the exogenous cation can assume the role played by Arg-127 in stabilizing the TS and in providing substrate selectivity at the P2 position.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 959-963 |
| Number of pages | 5 |
| Journal | Biochemistry® |
| Volume | 31 |
| Issue number | 4 |
| State | Published - 1992 |
Fingerprint
ASJC Scopus subject areas
- Biochemistry
Cite this
Transition-state characterization : A new approach combining inhibitor analogues and variation in enzyme structure. / Phillips, Margaret A.; Kaplan, Alan P.; Rutter, William J.; Bartlett, Paul A.
In: Biochemistry®, Vol. 31, No. 4, 1992, p. 959-963.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Transition-state characterization
T2 - A new approach combining inhibitor analogues and variation in enzyme structure
AU - Phillips, Margaret A.
AU - Kaplan, Alan P.
AU - Rutter, William J.
AU - Bartlett, Paul A.
PY - 1992
Y1 - 1992
N2 - A new strategy of potentially broad application for probing transition-state (TS) analogy in enzymatic systems is described in this paper. The degree to which a series of phosphonate inhibitors act as TS analogues of rat carboxypeptidase A1 has been determined for the wild-type enzyme, for the R127K, R127M, and R127A mutants, and for the R127A mutant in the presence of 0.5 M guanidine hydrochloride. The impact that the mutations have on the inverse second-order rate constants (Km/kcat) for substrate hydrolysis is mirrored by the effect on the inhibition constants (Ki) for the corresponding phosphonate inhibitors. These results demonstrate that the phosphonate moiety mimics some of the electronic as well as the geometric characteristics of the TS. A similar but distinctly separate correlation is observed for tripeptide analogues in comparison to analogues of the dipeptide Cbz-Gly-Phe, reflecting an anomalous mode of binding for the latter system. The selective rate increases and corresponding enhancement in inhibitor binding observed on addition of 0.5 M guanidine hydrochloride to the R127A mutant indicate that the exogenous cation can assume the role played by Arg-127 in stabilizing the TS and in providing substrate selectivity at the P2 position.
AB - A new strategy of potentially broad application for probing transition-state (TS) analogy in enzymatic systems is described in this paper. The degree to which a series of phosphonate inhibitors act as TS analogues of rat carboxypeptidase A1 has been determined for the wild-type enzyme, for the R127K, R127M, and R127A mutants, and for the R127A mutant in the presence of 0.5 M guanidine hydrochloride. The impact that the mutations have on the inverse second-order rate constants (Km/kcat) for substrate hydrolysis is mirrored by the effect on the inhibition constants (Ki) for the corresponding phosphonate inhibitors. These results demonstrate that the phosphonate moiety mimics some of the electronic as well as the geometric characteristics of the TS. A similar but distinctly separate correlation is observed for tripeptide analogues in comparison to analogues of the dipeptide Cbz-Gly-Phe, reflecting an anomalous mode of binding for the latter system. The selective rate increases and corresponding enhancement in inhibitor binding observed on addition of 0.5 M guanidine hydrochloride to the R127A mutant indicate that the exogenous cation can assume the role played by Arg-127 in stabilizing the TS and in providing substrate selectivity at the P2 position.
UR - http://www.scopus.com/inward/record.url?scp=0026581791&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0026581791&partnerID=8YFLogxK
M3 - Article
VL - 31
SP - 959
EP - 963
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 4
ER -