{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T15:15:08Z","timestamp":1791904508400,"version":"4.3.4"},"reference-count":0,"publisher":"Canadian Science Publishing","issue":"3","license":[{"start":{"date-parts":[[1969,3,1]],"date-time":"1969-03-01T00:00:00Z","timestamp":-26438400000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/www.nrcresearchpress.com\/page\/about\/CorporateTextAndDataMining"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Can. J. Biochem."],"published-print":{"date-parts":[[1969,3,1]]},"abstract":"<jats:p> The kinetics under consideration are those of a bacterial serine protease with the same \"active serine\" sequence as chymotrypsin, trypsin, and elastase, and with a single histidine residue in a sequence which closely matches the sequences around histidine-57 of chymotrypsin and the analogous histidine residues of trypsin and elastase. In agreement with previous evidence of an elastase-like specificity, esters of N-substituted, neutral, aliphatic L-amino acids proved to be good to excellent substrates for the \u03b1-enzyme; esters of arginine, tyrosine, and tryptophan were not hydrolyzed. The enzyme has a much higher activity than the pancreatopeptidases towards p-nitrophenyl acetate and p-nitrophenyl trimethyl acetate; the catalytic rate coefficient k<jats:sub>c<\/jats:sub> for the latter substrate is about fivefold greater than that of elastase.The catalytic properties match those of the pancreatopeptidases in the following respects. As demonstrated with N-acetyl-L-valine methyl ester as substrate, k<jats:sub>c<\/jats:sub> is dependent on an ionization with a pK<jats:sub>a<\/jats:sub> of 6.7 in water and 7.3 in H<jats:sup>2<\/jats:sup><jats:sub>2<\/jats:sub>O; \u0394 log (k<jats:sub>c<\/jats:sub>\/K<jats:sub>m<\/jats:sub>)\/\u0394pH for this ionization is equal to 1.0; k<jats:sub>c<\/jats:sub> is reduced 50% when H<jats:sub>2<\/jats:sub>O is replaced by H<jats:sup>2<\/jats:sup><jats:sub>2<\/jats:sub>O. These findings are consistent with a requirement for a single unprotonated histidine residue and general basic catalysis by that residue. The burst of p-nitrophenol in hydrolyses of p-nitrophenyl trimethyl acetate is proportional to [E]<jats:sub>0<\/jats:sub>; the magnitude of the proportionality factor and the rate of attainment of a steady state are consistent with the condition [Formula: see text], as in chymotrypsin kinetics. Thus the purely catalytic properties of the \u03b1-enzyme match those of chymotrypsin very closely. These findings do not support reaction mechanisms which require two catalytically functional histidine residues for such catalysis. The substrate-binding properties of the \u03b1-enzyme differ from those of chymotrypsin in that substrate binding does not depend on ionization of an N-terminal \u03b1-amino group; K<jats:sub>m<\/jats:sub> for the hydrolysis of N-acetyl-L-valine methyl ester is constant from pH 5 to pH 10 and enzymatic activity is unaffected by acetylation of the enzyme's \u03b1- and \u03b5-amino groups. K<jats:sub>s<\/jats:sub> for the hydrolysis of p-nitrophenyl trimethyl acetate is appreciably greater than the K<jats:sub>s<\/jats:sub> of elastase for this substrate.The chloromethyl ketones of glycine and valine did not inhibit the enzyme or alkylate its histidine residue. <\/jats:p>","DOI":"10.1139\/o69-047","type":"journal-article","created":{"date-parts":[[2009,12,17]],"date-time":"2009-12-17T22:10:42Z","timestamp":1261087842000},"page":"305-316","source":"Crossref","is-referenced-by-count":21,"title":["Kinetic properties of the \u03b1-lytic protease of <i>Sorangium<\/i> sp., a bacterial homologue of the pancreatopeptidases"],"prefix":"10.1139","volume":"47","author":[{"given":"H.","family":"Kaplan","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"D. R.","family":"Whitaker","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"155","container-title":["Canadian Journal of Biochemistry"],"original-title":[],"language":"en","link":[{"URL":"http:\/\/www.nrcresearchpress.com\/doi\/pdf\/10.1139\/o69-047","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2020,1,6]],"date-time":"2020-01-06T00:07:17Z","timestamp":1578269237000},"score":1,"resource":{"primary":{"URL":"http:\/\/www.nrcresearchpress.com\/doi\/10.1139\/o69-047"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1969,3,1]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1969,3,1]]}},"alternative-id":["10.1139\/o69-047"],"URL":"https:\/\/doi.org\/10.1139\/o69-047","relation":{},"ISSN":["0008-4018"],"issn-type":[{"value":"0008-4018","type":"print"}],"subject":[],"published":{"date-parts":[[1969,3,1]]}}}