Reaction of porcine pancreatic elastase with 7-substituted 3-alkoxy-4-chloroisocoumarins: design of potent inhibitors using the crystal structure of the complex formed with 4-chloro-3-ethoxy-7-guanidinoisocoumarin.Powers, J.C., Oleksyszyn, J., Narasimhan, S.L., Kam, C.M.
(1990) Biochemistry 29: 3108-3118
- PubMed: 2337582
- DOI: 10.1021/bi00464a030
- Primary Citation of Related Structures:
- PubMed Abstract:
- Effect of the 7-Amino Substituent on the Inhibitory Potency of Mechanism-Based Isocoumarin Inhibitors for Porcine Pancreatic and Human Neutrophil Elastases: A 1.85-Angstroms X-Ray Structure of the Complex between Porcine Pancreatic Elastase and 7-[(N-Tosylphenylalanyl)Amino]-4-Chloro-3-Methoxyisocoumarin
Hernandez, M.A., Powers, J.C., Glinski, J., Oleksyszyn, J., Vijayalakshmi, J., Meyerjunior, E.F.
(1992) J Med Chem 35: 1121
- Structural Study of Porcine Pancreatic Elastase Complexed with 7-Amino-3-(2-Bromoethoxy)-4-Chloroisocoumarin as a Nonreactivatable Doubly Covalent Enzyme-Inhibitor Complex
Vijayalakshmi, J., Meyerjunior, E.F., Kam, C.-M., Powers, J.C.
(1991) Biochemistry 30: 2175
- The 2.2-Angstrom Resolution X-Ray Crystal Structure of the Complex of Trypsin Inhibited by 4-Chloro-3-Ethoxy-7-Guanidinoisocoumarin: A Proposed Model of the Thrombin-Inhibitor Complex
Chow, M.M., Meyerjunior, E.F., Bode, W., Kam, C.-M., Radhakrishnan, R., Vijayalakshmi, J., Powers, J.C.
(1990) J Am Chem Soc 112: 7783
- Human Leukocyte and Porcine Pancreatic Elastase: X-Ray Crystal Structures, Mechanism, Substrate Specificity, and Mechanism-Based Inhibitors
Bode, W., Meyerjunior, E.F., Powers, J.C.
(1989) Biochemistry 28: 1951
- Crystal Structures of the Complex of Porcine Pancreatic Elastase with Two Valine-Derived Benzoxazinone Inhibitors
Radhakrishnan, R., Presta, L.G., Meyerjunior, E.F., Wildonger, R.
(1987) J Mol Biol 198: 417
- Stereospecific Reaction of 3-Methoxy-4-Chloro-7-Amino-Isocoumarin with Crystalline Porcine Pancreatic Elastase
Meyerjunior, E.F., Presta, L.G., Radhakrishnan, R.
(1985) J Am Chem Soc 107: 4091
The crystal structure of the acyl enzyme formed upon inhibition of porcine pancreatic elastase (PPE) by 4-chloro-3-ethoxy-7-guanidinoisocoumarin has been determined at a 1.85-A effective resolution. The chlorine atom is still present in this acyl enzyme, in contrast to the previously reported structure of the 7-amino-4-chloro-3-methoxyisocoumarin-PPE complex where the chlorine atom has been replaced by an acetoxy group ...
The crystal structure of the acyl enzyme formed upon inhibition of porcine pancreatic elastase (PPE) by 4-chloro-3-ethoxy-7-guanidinoisocoumarin has been determined at a 1.85-A effective resolution. The chlorine atom is still present in this acyl enzyme, in contrast to the previously reported structure of the 7-amino-4-chloro-3-methoxyisocoumarin-PPE complex where the chlorine atom has been replaced by an acetoxy group. The guanidino group forms hydrogen bonds with the carbonyl group and side-chain hydroxyl group of Thr-41, and the acyl carbonyl group has been twisted out of the oxyanion hole. Molecular modeling indicates that the orientation of the initial Michaelis enzyme-inhibitor complex is quite different from that of the acyl enzyme since simple reconstruction of the isocoumarin ring would result in unfavorable interactions with Ser-195 and His-57. Molecular models were used to design a series of new 7-(alkylureido)- and 7-(alkylthioureido)-substituted derivatives of 3-alkoxy-7-amino-4-chloroisocoumarin as PPE inhibitors. All the 3-ethoxyisocoumarins were better inhibitors than those in the 3-methoxy series due to better interactions with the S1 pocket of PPE. The best ureido inhibitor also contained a tert-butylureido group at the 7-position of the isocoumarin. Due to a predicted interaction with a small hydrophobic pocket on the surface of PPE, this isocoumarin and a related phenylthioureido derivative are among the best irreversible inhibitors thus far reported for PPE (kobs/[I] = 8100 M-1 s-1 and 12,000 M-1 s-1). Kinetic studies of the stability of enzyme-inhibitor complexes suggest that many isocoumarins are alkylating the active site histidine at pH 7.5 via a quinone imine methide intermediate, while at pH 5.0, the predominant pathway appears to be simple formation of a stable acyl enzyme derivative.
School of Chemistry, Georgia Institute of Technology, Atlanta 30332.