Keeping It in the Family

Gram-negative bacteria are known to create long-chain carbohydrates known as osmo-regulated periplasmic glucans (OPGs). These OPGs were once thought to be a by-product of low-solute concentrations, but new research suggests that they play a greater role in terms of bacterial pathogenicity – albeit with unclear explanations as to how and why. Indeed, knockout of OPG-associated genes is now known to hamper the pathogenicity of Xanthomonas campestris, Agrobacterium tumefaciens, and Salmonella enterica serovar Typhimuriu (1).

Researchers from the Tokyo University of Science shed even more light on the matter through structural and functional analyses of OPG-related genes in E. coli (1).

“We are focusing on finding novel carbohydrate-active enzymes (carbohydrate-synthesizing and degrading enzymes – referred to as ‘cazymes’), mainly from bacteria,” says Associate Professor Masahiro Nakajima.

“Carbohydrates play various important physiological roles, likely due to the tremendous range of potential chemical structures they can have,” he adds. “Consequently, there exists a wide array of enzymes for synthesizing and degrading these diverse carbohydrates.”

Studying these cazymes is not easy, says Nakajima. “Enzymatic methods primarily serve for carbohydrate synthesis. However, the ‘cazymes’ necessary for this synthesis need to be found by using the carbohydrates we intend to synthesize.”

There is a chicken-and-egg problem, Nakajima explains, adding that this quandary can be helped by the discovery of new, novel cazymes – something he and his team hope to be leaders in. “This paper represents the very first identification of the biochemical function in the MdoG superfamily, utilizing the superfamily proteins from E. coli,” he says.

Through their structural and functional analyses of target genes in E. coli, the researchers established that the proteins involved are β-1,2-glucanases. According to the paper, these proteins – EcOpgG and EcOpgD – showed different kinds of behavior from one another, and point to a previously unknown glycoside hydrolase family: GH186.