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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Healthy Processed Foods Research » Research » Publications at this Location » Publication #324898

Research Project: Defining, Measuring, and Mitigating Attributes that Adversely Impact the Quality and Marketability of Foods

Location: Healthy Processed Foods Research

Title: Structural analysis of a glycosides hydrolase family 42 cold-adapted ß-galactosidase from Rahnella sp. R3

item FAN, YUTING - Jiangnan University
item HUA, XIAO - Jiangnan University
item JIN, TENGCHUAN - University Of Science And Technology Of China
item FENG, YINGHUI - Jiangnan University
item YANG, RUIJIN - Jiangnan University
item Zhang, Yuzhu

Submitted to: RSC Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2016
Publication Date: 4/7/2016
Citation: Fan, Y., Hua, X., Jin, T., Feng, Y., Yang, R., Zhang, Y. 2016. Structural analysis of a glycosides hydrolase family 42 cold-adapted ß-galactosidase from Rahnella sp. R3. RSC Advances. 6(44):37362-37369. doi: 10.1039/C6RA04529D.

Interpretive Summary: The study reports the determination of the three-dimensional structure of a cold-adapted beta-galactosidase from the psychrophilic gram-negative bacterium Rahnella sp.R3 by X-crystallography and the site-directed mutagenesis analysis of important residues for its activity. The reported result can be used in constructing engineered beta-galactosidases with better activity and stability. Such an improved enzyme can be used in the efficient manufacturing of lactose-reduced milk and other dairy products that can be consumed by people with lactose intolerance. This, in turn, will reduce the negative impact on the marketing and utilization of milk products.

Technical Abstract: The ß-galactosidase isolated from a psychrotrophic bacterium, Rahnella sp. R3 (R-ß-Gal), exhibits high activity at low temperature. R-ß-Gal is a member of the glycoside hydrolases family 42 (GH42), and forms a 225 kDa trimeric structure in solution. The X-ray crystal structure of R-ß-Gal was determined at a 2.5 Å resolution. It is the first structure of a cold-adapted GH42 enzyme. In the crystallographic asymmetric unit, there were two homotrimers of the enzyme. Each monomer consists of three domains, an N-terminal catalytic domain which is a (ß/a)8 TIM barrel, a mixed ß-sheet and a-helices domain, and a C-terminal ß-sandwich structure. Two putative residues involved in catalysis, a proton donor E157 and a nucleophile E314, were superimposed well with the catalytic residues of other ß-galactosidases. Site-directed mutagenesis targeting these residues abolished the activity of the enzyme.