Kang Hee-Kyoung, Kim Young-Min, Kim Do-Man
School of Biological Sciences and Technology, Chonnam National University, Gwang-ju, Korea.
J Microbiol Biotechnol. 2008 Jun;18(6):1050-8.
A gene encoding a dextransucrase (dsrBCB4) that synthesizes only alpha-1,6-linked dextran was cloned from Leuconostoc mesenteroides B-1299CB4. The coding region consisted of an open reading frame (ORF) of 4,395 bp that coded a 1,465-amino-acids protein with a molecular mass 163,581 Da. The expressed recombinant DSRBCB4 (rDSRBCB4) synthesized oligosaccharides in the presence maltose or isomaltose as an acceptor, plus the products included alpha-1,6-linked glucosyl residues in addition to the maltosyl or isomaltosyl residue. Alignments of the amino acid sequence of DSRBCB4 with glucansucrases from Streptococcus and Leuconostoc identified conserved amino acid residues in the catalytic core that are critical for enzyme activity. The mutants D530N, E568Q, and D641N displayed a 98- to 10,000-fold reduction of total enzyme activity.
从肠系膜明串珠菌B - 1299CB4中克隆出一个编码仅合成α-1,6-连接葡聚糖的葡聚糖蔗糖酶（dsrBCB4）的基因。编码区由一个4395 bp的开放阅读框（ORF）组成，该阅读框编码一个1465个氨基酸的蛋白质，分子量为163581 Da。表达的重组DSRBCB4（rDSRBCB4）在以麦芽糖或异麦芽糖作为受体的情况下合成寡糖，产物除了麦芽糖基或异麦芽糖基残基外，还包括α-1,6-连接的葡萄糖基残基。DSRBCB4的氨基酸序列与来自链球菌属和明串珠菌属的葡聚糖蔗糖酶的比对确定了催化核心中对酶活性至关重要的保守氨基酸残基。突变体D530N、E568Q和D641N的总酶活性降低了98至10000倍。
