Substrate effects on the enzymatic activity of alpha-chymotrypsin in reverse micelles.
Six different substrates have been used for measuring the activity of alpha-chymotrypsin in reverse micelles formed by sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in isooctane. The substrates were glutaryl-Phe p-nitroanilide, succinyl-Phe p-nitroanilide, acetyl-Phe p-nitroanilide, succinyl-Ala-Ala-Phe p-nitroanilide, succinyl-Ala-Ala-Pro-Phe p-nitroanilide and acetyl-Trp methyl ester. It has been shown that the dependence of the kinetic constants (kcat and Km) on the water content of the system, on wo (= [H2O]/[AOT]), is different for the different substrates. This indicates that activity-wo profiles for alpha-chymotrypsin in reverse micelles not only reflect an intrinsic feature of the enzyme alone. For the p-nitroanilides it was found that the lower kcat (and the higher Km) in aqueous solution, the higher kcat as well as Km in reverse micelles. "Superactivity" of alpha-chymotrypsin could only be found with the ester substrate and with relatively "poor" p-nitroanilides. The presence of a negative charge in the substrate molecule is not a prerequisite for alpha-chymotrypsin to show "superactivity".
Mao
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Institut für Polymere, ETH-Zentrum, Zürich, Switzerland.
Walde
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D000595:Amino Acid Sequence; D002918:Chymotrypsin / Q000378:metabolism*; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D007700:Kinetics; D008823:Micelles; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology*; D013379:Substrate Specificity
D008823:Micelles; D009842:Oligopeptides; D002918:Chymotrypsin; D004121:Dimethyl Sulfoxide