4ipn

Publication Abstract from PubMed

The 6-phospho-beta-glucosidase BglA-2 (EC 3.2.1.86) from glycoside hydrolase family 1 (GH-1) catalyzes the hydrolysis of beta-1,4-linked cellobiose 6-phosphate (cellobiose-6'P) to yield glucose and glucose 6-phosphate. Both reaction products are further metabolized by the energy-generating glycolytic pathway. Here, we present the first crystal structures of the apo and complex forms of BglA-2 with thiocellobiose-6'P (a non-metabolizable analog of cellobiose-6'P) at 2.0 and 2.4 A resolution, respectively. Similar to other GH-1 enzymes, the overall structure of BglA-2 from Streptococcus pneumoniae adopts a typical (beta/alpha)8 TIM-barrel, with the active site located at the center of the convex surface of the beta-barrel. Structural analyses, in combination with enzymatic data obtained from site-directed mutant proteins, suggest that three aromatic residues, Tyr(126), Tyr(303), and Trp(338), at subsite +1 of BglA-2 determine substrate specificity with respect to 1,4-linked 6-phospho-beta-glucosides. Moreover, three additional residues, Ser(424), Lys(430), and Tyr(432) of BglA-2, were found to play important roles in the hydrolytic selectivity toward phosphorylated rather than non-phosphorylated compounds. Comparative structural analysis suggests that a tryptophan versus a methionine/alanine residue at subsite -1 may contribute to the catalytic and substrate selectivity with respect to structurally similar 6-phospho-beta-galactosidases and 6-phospho-beta-glucosidases assigned to the GH-1 family.

Structural Insights into the Substrate Specificity of a 6-Phospho-beta-glucosidase BglA-2 from Streptococcus pneumoniae TIGR4.,Yu WL, Jiang YL, Pikis A, Cheng W, Bai XH, Ren YM, Thompson J, Zhou CZ, Chen Y J Biol Chem. 2013 May 24;288(21):14949-58. doi: 10.1074/jbc.M113.454751. Epub, 2013 Apr 11. PMID:23580646^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.