Specificity of alpha-chymotrypsin with exposed carboxyl groups blocked.

Johnson, Phyllis E.; Stewart, James; Allen, Kim

doi:10.1016/s0021-9258(17)33594-9

Cited by 7 publications

(2 citation statements)

References 37 publications

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“…On hydroxylapatite in pH 6.8 phosphate, only one peak was obtained which accounted for 57% of the loaded protein. When assayed with BTEE, all three fractions showed enzymatic activity which was 30% of purified commercial -chymotrypsin, in agreement with the literature (Fersht and Sperling, 1973;Carraway et al, 1969;Abita et al, 1969;Johnson et at., 1976). In sedimentation equilibrium experiments, however, none of these products were found to dimerize, as shown in Table I and Figure 1.…”

Section: Resultssupporting

confidence: 91%

“…DIP-, TPCK-, tosyl-, and PMS-a-Ct were fully inactive, as was essentially the A-methylhistidine compound, the rate of which is known to be reduced by a factor of 103 to 10s (Nakagawa and Bender, 1970). The carboxyl-blocked enzyme had an activity of 30 to 40% relative to -chymotrypsin, in accordance with the literature (Fersht and Sperling, 1973;Carraway et al, 1969;Abita et al, 1969;Johnson et al, 1976). Met-192-sulfoxide-a-Ct was 40% active in agreement with Taylor et al (1973).…”

Section: Resultssupporting

confidence: 86%

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Low pH dimerization of chymotrypsin in solution

Gorbunoff¹,

Timasheff²

1978

Biochemistry

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The mechanism of the acid dimerization of alpha-chymotrypsin in solution was reexamined using a number of chemical derivatives. Blocking of the carboxyl of Tyr-146, while that of ASP-64 remained free, eliminated completely the ability of alpha-chymotrypsin to dimerize, as did methylation of His-57. O-Acetylation of Tyr-146 reduced the dimerization constant to that of gamma-chymotrypsin, and deacetylation of the other accessible tyrosines did not affect the dimerization. It is concluded that the mechanism proposed by Aune and Timasheff [Aune, K.C., and Timasheff, S.N.(1971) Biochemistry 10, 1609-1617] for the solution dimerization which involves the electrostatic interaction between the His-57 imidazolium ring and the terminal carboxyl of Tyr-146 is still most consistent with all the experimental observations. The interactions in dilute solution may differ somewhat from those observed in crystals. In particular, the two intermolecular bridges formed by sulfate ions in crystals cannot be present in solution.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 86%

Low pH dimerization of chymotrypsin in solution

Gorbunoff¹,

Timasheff²

1978

Biochemistry

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The carboxypeptidase Y catalysed hydrolysis of indoleacryloyl imidazole

Martin

Oliver

Johansen

et al. 1980

Carlsberg Res. Commun.

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Reaction of carboxypeptidase Y with the chromophoric substrate indoleacryloyl imidazole was found to proceed via an acylenzyme intermediate, indoleacryloyl-carboxypeptidase Y, which exhibited a blue shift in 7tmax with increasing pH. Ag + ions effectively prevented the acylation of the enzyme, while Hg + + ions were found to retard the deacylation of the acyl enzyme intermediate. Cyanylation of the single thiol function in carboxypeptidase Y could be readily achieved in buffer media (pH 7.0) containing 3.3 M urea. Such modification had little effect on the activity of the enzyme towards its typical peptide and ester substrates, suggesting that the thiol group does not participate directly in the catalytic mechanism.

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