Journal article
The formation and activities of substituted phenacylchymotrypsins
Biochimica et biophysica acta, Vol.191(3), pp.677-685
1969
DOI: 10.1016/0005-2744(69)90361-1
PMID: 5363989
Abstract
1.|The preparation of derivatives of α-chymotrypsin with p-nitrophenacyl bromide, phenacyl bromide and p-methoxyphenacyl bromide is described. 2. For the p-nitrophenacyl derivative, the new 350-nm absorption is pH independent from pH 2.88 to 11.25, mitigating against a major change in environment at the new chromophore over this range. 3. The enzyme derivatives (likely at Met-192) show different decreased but definite catalytic activities towards substrates of α-chymotrypsin. In each case, this activity is due to the modified enzyme itself. 4. Phenacyl- and p-methoxyphenacylchymotrypsin show generally increased dissociation constants and decreased catalytic constants. Below pH 8.5, p-nitrophenacylchymotrypsin towards ethyl-N-acetyl-L-tryptophanate has only decreased kcat values compared to native enzyme, K, being unaltered. The pH dependencies of kcitt below pH 8.5 and K, over the entire range are identical for parent and nitro- phenacyl enzymes. Above pH 8.5, k cat for the enzyme derivative increases and is still rising at pH IO, having reached over twice its value at pH 8.5. The effect is reversible. 5. These results are taken to indicate that the conformational change occurring in a-chymotrypsin at pK 9 occurs for the nitrophenacyl enzyme as well, but, in the latter case, it reverses the original inhibition of kcat by the nitrophenacyl group
Details
- Title: Subtitle
- The formation and activities of substituted phenacylchymotrypsins
- Creators
- M J GibianP A RubensteinW H Ficklin
- Resource Type
- Journal article
- Publication Details
- Biochimica et biophysica acta, Vol.191(3), pp.677-685
- Publisher
- Netherlands
- DOI
- 10.1016/0005-2744(69)90361-1
- PMID
- 5363989
- ISSN
- 0006-3002
- eISSN
- 1878-2434
- Language
- English
- Date published
- 1969
- Academic Unit
- Stead Family Department of Pediatrics; Biochemistry and Molecular Biology; Internal Medicine
- Record Identifier
- 9984025251602771
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