PDBsum entry 8est

Hydrolase(serine proteinase)

PDB id: 8est

Contents

Protein chain

240 a.a. *

Ligands

SO4

GIS

Metals

_CA

Waters ×169

* Residue conservation analysis

PDB id:

8est

Name:

Hydrolase(serine proteinase)

Title:

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-guanidino- isocoumarin

Structure:

Porcine pancreatic elastase. Chain: e. Engineered: yes

Source:

Sus scrofa. Pig. Organism_taxid: 9823

Resolution:

1.78Å R-factor: 0.170

Authors:

R.Radhakrishnan,J.C.Powers,E.F.Meyerjunior

Key ref:

J.C.Powers et al. (1990). 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. Biochemistry, 29, 3108-3118. PubMed id: 2337582 DOI: 10.1021/bi00464a030

Date:

21-Feb-90 Release date: 15-Oct-92

Protein chain

P00772  (CELA1_PIG) -  Chymotrypsin-like elastase family member 1 from Sus scrofa

Seq: 266 a.a.

Struc: 240 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.3.4.21.36 - pancreatic elastase.
• Reaction: Hydrolysis of proteins, including elastin. Preferential cleavage: Ala-|-Xaa.

DOI no: 10.1021/bi00464a030

Biochemistry 29:3108-3118 (1990)

PubMed id: 2337582

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.

J.C.Powers, J.Oleksyszyn, S.L.Narasimhan, C.M.Kam.

ABSTRACT

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the previously reported structure of the 7-amino-4-chloro-3-methoxyisocoumarin-PPE complex where the chlorine atom has been replaced by an acetoxy group.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.