@article{oai:rakuno.repo.nii.ac.jp:00005186,
 author = {Tagami, Takayoshi and Miyano, Eri and Sadahiro, Juri and Okuyama, Masayuki and IWASAKI, Tomohito and 岩﨑, 智仁 and Kimura, Atsuo},
 issue = {32},
 journal = {The Journal of Biological Chemistry},
 month = {Aug},
 note = {Article, The actinobacterium Kribbella flavida NBRC 14399^T produces cyclobis-(1→6)-α-nigerosyl (CNN), a cyclic glucotetraose with alternate α-(1→6)- and α-(1→3)-glucosidic linkages, from starch in the culture medium. We identified gene clusters associated with the production and intracellular catabolism of CNN in the K. flavida genome. One cluster encodes 6-α-glucosyltransferase and 3-α-isomaltosyltransferase, which are known to coproduce CNN from starch. The other cluster contains four genes annotated as a transcriptional regulator, sugar transporter, glycoside hydrolase family (GH) 31 protein (Kfla1895), and GH15 protein (Kfla1896). Kfla1895 hydrolyzed the α-(1→3)-glucosidic linkages of CNN and produced isomaltose via a possible linear tetrasaccharide. The initial rate of hydrolysis of CNN (11.6 s^<−1>) was much higher than that of panose (0.242 s^<−1>), and hydrolysis of isomaltotriose and nigerose was extremely low. Because Kfla1895 has a strong preference for the α-(1→3)-isomaltosyl moiety and effectively hydrolyzes the α-(1→3)-glucosidic linkage, it should be termed 1,3-α-isomaltosidase. Kfla1896 effectively hydrolyzed isomaltose with liberation of β-glucose, but displayed low or no activity toward CNN and the general GH15 enzyme substrates such as maltose, soluble starch, or dextran. The k_<cat>/K_m for isomaltose (4.81 ± 0.18^<s−1> mm^<−1>) was 6.9- and 19-fold higher than those for panose and isomaltotriose, respectively. These results indicate that Kfla1896 is a new GH15 enzyme with high substrate specificity for isomaltose, suggesting the enzyme should be designated an isomaltose glucohydrolase. This is the first report to identify a starch-utilization pathway that proceeds via CNN.},
 pages = {16438--16447},
 title = {Two Novel Glycoside Hydrolases Responsible for the Catabolism of Cyclobis-(1→6)-α-nigerosyl},
 volume = {291},
 year = {2016}
}