Crystallographic and NMR Studies of the Serine Proteases

Abstract

Since the serine proteases form the most thoroughly understood family of enzymes, it is of some interest to consider what the two principal physical techniques of studying enzymes, crystallography and nuclear magnetic resonance (NMR), have told us about the details of their enzymatic mechanism. Due to limitations of space, this review cannot be compre hensive nor can it describe the history of the current ideas concerning the action of these enzymes.Two major issues have attracted the attention of both diffraction and NMR studies in the past ten years: the first concerns the nature and the role of the catalytic triad of serine 195, histidine 57, and aspartic acid 102; the second is the possibility of induced distortions upon complexa tion of either the substrate or the enzyme. We first consider these issues in terms of the crystallographic studies and then of the NMR experi ments. Finally, we interpret these results in terms of a detailed structural and electronic mechanism. Our conclusions, subject to further test, are that the triad does not exist in the resting state of the enzyme because the serine-histidine bond is not formed. However, we suggest that this bond does form upon complexation with substrates allowing the triad to play an important role in catalysis.

Serine carboxypeptidases. A review

“…in the absence of substrate, but crystallographic studies on the complex between trypsin and pancreatic trypsin inhibitor have suggested that a hydrogen bond between the seryl and histidyl residues does exist (83) and NMR studies of this enzyme-inhibitor complex imply partial formation of an alkoxide anion on the seryi residue (121). These results are in conflict with those obtained by KRAUT and coworkers ( 108,132), suggesting that important differences exist between "resting" and "working" enzyme (174), such that observations with resting enzyme are insufficient to explain important aspects of its function.…”

Structure of a complex of the potent and specific inhibitor BW284C51 withTorpedo californicaacetylcholinesterase

“…The three-dimensional structure of Torpedo californica AChE (TcAChE) revealed that its active site is located at the bottom of a long and narrow cavity lined with aromatic residues, which was named the`active-site gorge' (Sussman et al, 1991). The active site contains a catalytic triad and an oxyanion hole, similar to those found in other serine hydrolases (Steitz & Shulman, 1982), an acyl pocket which recognizes the acetyl group (Harel et al, 1992) and a so-called`anionic site', which recognizes the quaternary group of ACh. Surprisingly, the principal component of this anionic site is not a cluster of negative charges, as previously postulated (Nolte et al, 1980), but rather the indole moiety of Trp84, which makes a %±cation interaction (Dougherty & Stauffer, 1990;Felder et al, 2001) with the quaternary group of ACh (Sussman et al, 1991).…”

Serine proteases: An ab initio molecular dynamics study

“…[1][2][3] A typical example in this respect is constituted by the enzyme family of serine proteases (SPs). [3][4][5][6][7][8][9][10][11][12][13] SPs use the catalytic triad (Ser195-His57-Asp102) to catalyze the hydrolysis of peptides (Fig. 1a).…”