Exopolysaccharide Alginate Synthesis in Pseudomonas Aeruginosa : Enzymology and Regulation of Gene Expression

Abstract

e p a r t m e n t of M i c r o b i o l o g y a n d I m m u n o l o g y ( M I C 790),

Alginate Lyase (AlgL) Activity Is Required for Alginate Biosynthesis in Pseudomonas aeruginosa

“…algC, which is also involved in lipopolysaccharide biosynthesis (9), is located outside of this cluster and is expressed from its own promoter (27). Alginate biosynthesis begins in the cytoplasm with fructose-6-phosphate, which is converted to GDP-mannuronic acid via a series of steps involving AlgA, AlgC, and AlgD (see reference 24 for review) and then transported across the periplasmic membrane, possibly by Alg8 and Alg44 (24). Alg8, due to its resemblance to ␤-glycosyltransferases (21), is considered to be a good candidate for the polymerization of GDPmannuronic acid residues into a poly(M) chain, but AlgK might also be involved (12).…”

“…Most of the alginate biosynthetic genes, including algD, alg8, alg44, algK, algE, algG, algX, algL, algI, algJ, algF, and algA, are found in a chromosomal gene cluster which functions as an operon controlled by the algD promoter (1,24). algC, which is also involved in lipopolysaccharide biosynthesis (9), is located outside of this cluster and is expressed from its own promoter (27).…”

Role of two phosphohexomutase genes in glycogen synthesis in Synechocystis sp. PCC6803

“…Slr1334 appeared to be essential for the growth of Synechocystis. In bacteria, PMM could be involved in the synthesis of lipopolysaccharide [3] or exopolysaccharide [2]. However, lipopolysaccharide [25] and probably exopolysaccharide are not essential for the growth of cyanobacteria.…”

“…Despite differences in substrate specificity, phosphoglucomutase (PGM), phosphoglucomutase/phosphomannomutase bifunction enzyme (PGM/PMM), phosphoglucosamine mutase (PNGM) and phosphoacetylglucosamine mutase (PAGM) catalyze the reactions in a similar mechanism: via a 1,6-biphosphohexose intermediate [1]. In bacteria, PGM that converts glucose-6-phosphate (G-6-p) into glucose-1-phosphate (G-1-p) is required for synthesis of glycogen and other poly-or oligosaccharides, PMM that uses M (mannose)-6-p as the substrate is involved in biosynthesis of lipopolysaccharide and exopolysaccharide [2,3].…”

Activated Sugar Precursors: Biosynthetic Pathways and Biological Roles of an Important Class of Intermediate Metabolites in Bacteria

“…Both the GMdh and UGD enzyme activities are mechanistically similar, using a unique active site to catalyze the two-step conversion of an alcohol group to the corresponding acid, via a thiohemiacetal intermediate. GDP-D-mannuronic acid is the activated sugar precursor for alginate polymerization in P. aeruginosa, which is a partially O-acetylated linear polymer of D-mannuronic acid and Lguluronic acid, linked via -1,4 glycosidic bonds (Shankar et al, 1995). In the case of the P. aeruginosa alginate, after polymerization, some D-mannuronic acid residues can be further converted to L-guluronic acid by the extracellular enzyme activity polymannuronic acid C-5-epimerase (Jerga et al, 2006).…”