The glgB-encoded glycogen branching enzyme is essential for glycogen accumulation in Corynebacterium glutamicum

Abstract

Corynebacterium glutamicum transiently accumulates glycogen as carbon capacitor during the early exponential growth phase in media containing carbohydrates. In some bacteria glycogen is synthesized by the consecutive action of ADP-glucose pyrophosphorylase (GlgC), glycogen synthase (GlgA) and glycogen branching enzyme (GlgB). GlgC and GlgA of C. glutamicum have been shown to be necessary for glycogen accumulation in this organism. However, although cg1381 has been annotated as the putative C. glutamicum glgB gene, cg1381 and its gene product have not been characterized and their role in transient glycogen accumulation has not yet been investigated. We show here that the cg1381 gene product of C. glutamicum catalyses the formation of α-1,6-glycosidic bonds in polysaccharides and thus represents a glycogen branching enzyme. RT-PCR experiments revealed glgB to be co-transcribed with glgE, probably encoding a maltosyltransferase. Promoter activity assays with the glgE promoter region revealed carbon-source-dependent expression of the glgEB operon. Characterization of the growth and glycogen content of glgB-deficient and glgB-overexpressing strains showed that the glycogen branching enzyme GlgB is essential for glycogen formation in C. glutamicum. Taken together these results suggest that an interplay of the enzymes GlgC, GlgA and GlgB is not essential for growth, but is required for synthesis of the transient carbon capacitor glycogen in C. glutamicum.

Crystal Structures of Escherichia coli Branching Enzyme in Complex with Linear Oligosaccharides

“…(16)(17)(18)(19)(20) It has also been suggested that bacteria make distinct forms of glycogen depending on their environment. Bacteria like Enterobacteria, that live primarily in other organisms where food is relatively plentiful, tend to have glycogen made up of longer average glucan chains, while organisms that must survive for extended periods outside of a host, in relatively hostile environments, tend to produce glycogen with much shorter average glucan chains.…”

The α-Glucan Phosphorylase MalP of Corynebacterium glutamicum Is Subject to Transcriptional Regulation and Competitive Inhibition by ADP-Glucose

“…In a similar manner, transcription of the genes glgC, glgA, and glgB for glycogen synthesis is induced in cultivations with glucose and repressed in cultivations with acetate (42,44). The two global regulators RamA and RamB are involved in the control of glgC and/or glgA transcription; however, the substrate-dependent transcriptional control of these two genes is brought about by an as-yet-unknown regulator (44).…”

“…For quantification of ␣-glucan degradation products, the bicinchoninic acid assay was used as described previously (42). Glucose solutions (0 to 25 M) were used for the calibration.…”

“…In cultivations of C. glutamicum on glucose, large amounts of glycogen are synthesized in the early exponential growth phase from glc-6-P by the consecutive action of phosphoglucomutase (Pgm), ADP-glucose pyrophosphorylase (GlgC), glycogen synthase (GlgA), and glycogen branching enzyme (GlgB) (34,40,42,43). Degradation of glycogen takes place in C. glutamicum before the entry of the stationary phase and proceeds by the concerted action of the glycogen debranching enzyme (GlgX) and the two ␣-glucan phosphorylases designated MalP and GlgP (41,43).…”

Expression and Biochemical Characterization of a Thermostable Branching Enzyme from <b><i>Geobacillus thermoglucosidans</i></b>

“…Branching enzymes have been described in a variety of organisms, including plants [Carciofi et al, 2012;Huang et al, 2013;Kang et al, 2013;Yandeau-Nelson et al, 2011], animals [Lee et al, 2011;Ward et al, 2004;Ziemssen et al, 2000], fungi [Matsumoto et al, 1990] and bacteria [Roussel et al, 2013;Seibold et al, 2011]. However, only a few of these branching enzymes have been shown to be active at high temperatures.…”