Van Rijssel M, Smidt MP, Van Kouwen G, Hansen TA. Involvement of an Intracellular Oligogalacturonate Hydrolase in Metabolism of Pectin by Clostridium thermosaccharolyticum.
Appl Environ Microbiol 2010;
59:837-42. [PMID:
16348892 PMCID:
PMC202197 DOI:
10.1128/aem.59.3.837-842.1993]
[Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enzymes pectin methylesterase and polygalacturonate hydrolase, which are responsible for the initial steps of pectin degradation by Clostridium thermosaccharolyticum, were shown to be induced on the polymeric substrates pectin and pectate, as well as on oligogalacturonates, and to be repressed in the presence of glucose. The digalacturonate and trigalacturonate produced by the extracellular pectin methylesterase-polygalacturonate hydrolase complex were transported across the cytoplasmic membrane and hydrolyzed by an inducible oligogalacturonate hydrolase to galacturonate. The oligogalacturonate hydrolase was separated from the polygalacturonate hydrolase and characterized. Its temperature optimum was 65 degrees C, and its pH optimum was 6. The native molecular size was 90 kDa, and the enzyme was stable for more than 1 h at 65 degrees C. The maximum reaction rate on oligomers decreased with the increasing degree of polymerization. Galacturonate was released by hydrolysis from the nonreducing end of the oligomer. The amounts of pectinolytic enzymes produced were all strictly correlated to the amount of biomass formed. Galacturonate was metabolized via a modified Entner-Doudoroff route.
Collapse