Abstract: Isomannanase is the key enzymes of making probiotics-Mannan oligosaccharides （MOS）. A Bacillus subtilis K-6 strain that can secret isomannanase preserved in the laboratory was induced by UV. The mutation mech- anism of a positive mutant K-6-9 was studied. Initial Bacillus subtilis K-6 and positive mutant Bacillus subtilis K-6- 9 was cloned and expressed,then analyzed the gene and protein sequence of isomannanase mutation gene by bioin- fonnatics,the total base mutation and amino acids mutations of the mutants obtained. The results indicated that the total base mutation rate of mutants was 1.02%, the types of base changes included base transition and transversion. Among the 11 base mutations that had detected, the frequency of base transitions （54.5 % ） was 1.2 times higher that the base transversions （45.5 % ）, the transitions between C and T accounted for largest proportion, A-G transi- tions and A-T transversions were also interchanged at high frequency. After of protein sequences, there were two point mutation forms, which were Pro （conservative amino acid）-Ser（ non-conservative amino acid） at 21nt and Ser （non-conservative amino acid）-Glu （conservative amino acid） at 23nt. From a comprehensive and comparative data analysis,the mutual mutations between conservative amino acid and non-conservative amino acid may play an im- portant role in proteins assemble correctly and execute their function effectively.

Key words: Isomannanase, UV-mutation, Cloning Mutantion

CLC Number: 

• Q78