title: Hydrolytic and phosphorolytic metabolism of cellobiose by the marine aerobic bacterium Saccharophagus degradans 2-40T.
abstract: Saccharophagus degradans 2-40 is a marine gamma proteobacterium that can produce polyhydroxyalkanoates from lignocellulosic biomass using a complex cellulolytic system. This bacterium has been annotated to express three surface-associated β-glucosidases (Bgl3C, Ced3A, and Ced3B), two cytoplasmic β-glucosidases (Bgl1A and Bgl1B), and unusual for an aerobic bacterium, two cytoplasmic cellobiose/cellodextrin phosphorylases (Cep94A and Cep94B). Expression of the genes for each of the above enzymes was induced when cells were transferred into a medium containing Avicel as the major carbon source except for Bgl1B. Both hydrolytic and phosphorolytic degradation of cellobiose by crude cell lysates obtained from cellulose-grown cells were demonstrated and all of these activities were cell-associated. With the exception of Cep94B, each purified enzyme exhibited their annotated activity upon cloning and expression in E. coli. The five β-glucosidases hydrolyzed a variety of glucose derivatives containing β-1, (2, 4, or 6) linkages but did not act on any α-linked glucose derivatives. All but one β-glucosidases exhibited transglycosylation activity consistent with the formation of an enzyme-substrate intermediate. The biochemistry and expression of these cellobiases indicate that external hydrolysis by surface-associated β-glucosidases coupled with internal hydrolysis and phosphorolysis are all involved in the metabolism of cellobiose by this bacterium.
authors.affiliation: Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
authors.forename: Haitao
authors.initials: H
authors.lastname: Zhang
authors.forename: Young Hwan
authors.initials: YH
authors.lastname: Moon
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Watson
authors.forename: Maxim
authors.initials: M
authors.lastname: Suvorov
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Santos
authors.forename: Corinn A
authors.initials: CA
authors.lastname: Sinnott
authors.forename: Steven W
authors.initials: SW
authors.lastname: Hutcheson
mesh_terms: D034241:Alteromonadaceae / Q000235:genetics / Q000378:metabolism*; D001420:Bacteria, Aerobic / Q000378:metabolism; D002475:Cellobiose / Q000378:metabolism*; D002482:Cellulose / Q000378:metabolism; D043366:Cellulose 1,4-beta-Cellobiosidase / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D010766:Phosphorylation; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism
chemical_list: D002475:Cellobiose; D002482:Cellulose; D005964:Glucosyltransferases; C034714:cellobiose phosphorylase; C105024:cellodextrin phosphorylase; D001617:beta-Glucosidase; D043366:Cellulose 1,4-beta-Cellobiosidase