Active Site Interactions in Fluorine-Labeled a-Chymotrypsin

ACTIVE SITE INTERACTIONS IN FLUORINE-LABELED a-CHYMOTRYPSIN 

The sidechain of methionine-192 plays an important role in a-chymotrypsin, being implicated in both the activation of the enzyme from its zymogen and the binding and orientation of a-chymotrypsin substrates during catalysis. X-ray diffraction studies reveal that the sidechain may act as a lid over a hydrophobic sidechain binding pocket known as the tosyl hole. Modification of the sidechain of Met-192 therefore has kinetic consequences thus the addition of an aromatic moiety allows it to bind in the tosyl pocket and to compete for this site with substrate or inhibitor. The behavior of such an aromatic moiety may conveniently be followed via 

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