کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1179733 | 962795 | 2006 | 11 صفحه PDF | دانلود رایگان |

Dextran glucosidase from Streptococcus mutans (SMDG) and Bacillus oligo-1,6-glucosidases, members of glycoside hydrolase family 13 enzymes, have the high sequence similarity. Each of them is specific to α-1,6-glucosidic linkage at the non-reducing end of substrate to liberate glucose. The activities toward long isomaltooligosaccharides were different in both enzymes, in which SMDG and oligo-1,6-glucosidase showed high and low activities, respectively. We determined the structural elements essential for high activity toward long-chain substrate. From conformational comparison between SMDG and B. cereus oligo-1,6-glucosidase (three-dimensional structure has been solved), Trp238 and short β → α loop 4 of SMDG were considered to contribute to the high activity to long-chain substrate. W238A had similar kcat/Km value for isomaltotriose to that for isomaltose, suggesting that the affinity of subsite +2 was decreased by Trp238 replacement. Trp238 mutants as well as the chimeric enzyme having longer β → α loop 4 of B. subtilis oligo-1,6-glucosidase showed lower preference for long-chain substrates, indicating that both Trp238 and short β → α loop 4 were important for high activity to long-chain substrates.
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1764, Issue 4, April 2006, Pages 688–698