title: A novel polygalacturonic acid bioflocculant REA-11 produced by Corynebacterium glutamicum: a proposed biosynthetic pathway and experimental confirmation.
abstract: Corynebacterium glutamicum CCTCC M201005 produces a novel polygalacturonic acid bioflocculant, REA-11, consisting of galacturonic acid as the main structural unit. A biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 was proposed. Evidence for the biosynthetic pathway was provided by: (1) analyzing the response upon addition of UDP-glucose to the culture medium; (2) detecting the presence of several key intermediates in the pathway; and (3) correlating the activities of several key enzymes involved in the pathway with the yields of polygalacturonic acid. The production of polygalacturonic acid was improved by 24%, while the activities of UDP-galactose epimerase and UDP-galactose dehydrogenase were improved by 200% and 50%, respectively, upon addition of 100 microM UDP-glucose. In addition, the key intermediates in the proposed biosynthetic pathway, such as UDP-glucose, UDP-galactose, and UDP-glucuronic acid, were detected in cell-free extracts. Furthermore, the activities of UDP-glucose pyrophosphorylase (R2=0.97), UDP-galactose epimerase (R2=0.75) and UDP-galactose dehydrogenase (R2=0.89) were well correlated with the yields of polygalacturonic acid when different sugars were used as sole carbon sources. Therefore, the biosynthetic pathway of REA-11 in C. glutamicum CCTCC M201005 starts from phosphate-1-glucose, which was then converted to UDP-glucose by UDP-pyrophosphorylase. Predominantly, the UDP-glucose was converted to UDP-galactose by UDP-galactose epimerase; the latter was further converted to UDP-galacturonic acid by UDP-galactose dehydrogenase, which was presumably polymerized to polygalacturonic acid bioflocculant REA-11 by an unknown glucosyltransferase and a polymerase.
authors.affiliation: The Key Laboratory of Industrial Biotechnology, Ministry of Education, Southern Yangtze University, 214036 Wuxi, PR China.
authors.forename: Y
authors.initials: Y
authors.lastname: Li
authors.forename: N
authors.initials: N
authors.lastname: He
authors.forename: H
authors.initials: H
authors.lastname: Guan
authors.forename: G
authors.initials: G
authors.lastname: Du
authors.forename: J
authors.initials: J
authors.lastname: Chen
mesh_terms: D003352:Corynebacterium / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology*; D003470:Culture Media; D005427:Flocculation; D010368:Pectins / Q000378:metabolism*; D014531:Uridine Diphosphate Galactose / Q000378:metabolism; D014532:Uridine Diphosphate Glucose / Q000378:metabolism; D014539:Uridine Diphosphate Sugars / Q000378:metabolism
chemical_list: D003470:Culture Media; D014539:Uridine Diphosphate Sugars; D014531:Uridine Diphosphate Galactose; C050306:UDP-galacturonic acid; D010368:Pectins; D014532:Uridine Diphosphate Glucose; C003181:polygalacturonic acid