| 释义 |
exoenzyme, n. Biochem.|ˈɛksəʊˌɛnzaɪm|
Also exo-enzyme.
[f. exo- + enzyme n.]
1. An enzyme which is secreted or acts extracellularly.
1908H. M. Vernon Intracellular Enzymes 1 Exo-enzymes..are found in many of the secretions of living organisms. 1926Waksman & Davison Enzymes ii. 14 In the case of animals the free (exo) enzymes are formed and secreted by special organs (glands). 1942Adv. Enzymol. II. 244 The conventional view is that an exo-enzyme brings about hydrolysis of the cellulose molecule with consequent liberation of glucose, which is subsequently dissimilated intercellularly. 1976Ann. Rev. Microbiol. XXX. 42 Many exoenzymes appear to be subject to control by end product inhibition and catabolite repression. 1984Holtzman & Novikoff Cells & Organelles (ed. 3) iii. ii. 330 Bacteria also produce exoenzymes that are secreted to the extracellular environment or into the periplasmic space of Gram-negative forms.
2. An enzyme that acts on the ends of a substrate molecule.
1955Jrnl. Biol. Chem. CCXIII. 244 These data showed that the glucuronidase is an ‘exo’ enzyme and does not hydrolyze internal linkages. 1958Dixon & Webb Enzymes v. 228 The endo- and exo-enzymes co-operate very effectively in protein digestion, in which it may be said that the main function of the former is to produce a large number of free ends at which the latter can act. 1972Roberts & Boothroyd Fund. Plant Path. vii. 121 The chain-splitting pectolytic enzymes, whether hydrolytic or transeliminative, may occur as endoenzymes or exoenzymes. 1982T. M. Devlin Textbk. Biochem. xxiv. 1159 Most of the surface oligosaccharidases are exoenzymes which clip off one monosaccharide at a time from the nonreducing end. |