Background: To identify the critical amino acid residues that
contribute to the high enzyme activity and good thermostability of
Yersinia enterocolitica subsp. palearctica (Y. NSN), 15 mutants of Y.
NSN were obtained by site-directed mutagenesis in this study. And their
enzyme activity and thermostability were assayed. Effect of several
factors on the enzyme activity and thermostability of Y. NSN, was also
investigated. Results: The results showed that the I203F and D264E
mutants retained approximately 75% and 70% enzyme activity,
respectively, compared to the wild-type enzyme. In addition to the
I203F and D264E mutants, the mutant E202A had an obvious influence on
the thermostability of Y. NSN. According to the analysis of enzyme
activity and thermostability of Y. NSN, we found that Glu202, Ile203
and Asp264 might be the key residues for its high enzyme activity and
good thermostability. Conclusions: Among all factors affecting enzyme
activity and thermostability of Y. NSN, they failed to explain the
experimental results well. One reason might be that the enzyme activity
and thermostability of Y. NSN were affected not only by a single factor
but also by the entire environment