Study of two glycosyltransferases related to polysaccharide biosynthesis in Rhodococcus jostii RHA1

Author:

Cereijo Antonela Estefania1,Ferretti María Victoria1,Iglesias Alberto Alvaro1ORCID,Álvarez Héctor Manuel2,Asencion Diez Matías Damian1ORCID

Affiliation:

1. Laboratorio de Enzimología Molecular , 603337 Instituto de Agrobiotecnología del Litoral (UNL-CONICET) & Facultad de Bioquímica y Ciencias Biológicas , Santa Fe , Argentina

2. Instituto de Biociencias de la Patagonia (INBIOP) , 28226 Universidad Nacional de la Patagonia San Juan Bosco y CONICET , Km 4-Ciudad Universitaria 9000 , Comodoro Rivadavia , Chubut , Argentina

Abstract

Abstract The bacterial genus Rhodococcus comprises organisms performing oleaginous behaviors under certain growth conditions and ratios of carbon and nitrogen availability. Rhodococci are outstanding producers of biofuel precursors, where lipid and glycogen metabolisms are closely related. Thus, a better understanding of rhodococcal carbon partitioning requires identifying catalytic steps redirecting sugar moieties to storage molecules. Here, we analyzed two GT4 glycosyl-transferases from Rhodococcus jostii (RjoGlgAb and RjoGlgAc) annotated as α-glucan-α-1,4-glucosyl transferases, putatively involved in glycogen synthesis. Both enzymes were produced in Escherichia coli cells, purified to homogeneity, and kinetically characterized. RjoGlgAb and RjoGlgAc presented the “canonical” glycogen synthase activity and were actives as maltose-1P synthases, although to a different extent. Then, RjoGlgAc is a homologous enzyme to the mycobacterial GlgM, with similar kinetic behavior and glucosyl-donor preference. RjoGlgAc was two orders of magnitude more efficient to glucosylate glucose-1P than glycogen, also using glucosamine-1P as a catalytically efficient aglycon. Instead, RjoGlgAb exhibited both activities with similar kinetic efficiency and preference for short-branched α-1,4-glucans. Curiously, RjoGlgAb presented a super-oligomeric conformation (higher than 15 subunits), representing a novel enzyme with a unique structure-to-function relationship. Kinetic results presented herein constitute a hint to infer on polysaccharides biosynthesis in rhodococci from an enzymological point of view.

Funder

Fondo para la Investigación Científica y Tecnológica

Consejo Nacional de Investigaciones Científicas y Técnicas

Publisher

Walter de Gruyter GmbH

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