Cover illustration A lipase from Pseudomonas aeruginosa was subjected to directed evolution for increased amidase activities. The amino acid residue 252 adjacent to the catalytic His251 was found to be a "hot spot" for selectively increasing the amidase activity. The increase in the amidase activity of a mutant (Phe252) was caused by the increase in the catalytic efficiency (kcat). Here the substratebinding site of this mutant in complex with a phosphonate inhibitor is shown to highlight the location of Phe252 (red) and the catalytic His251 (blue) in the vicinity of the leaving group amine, suggesting that Phe252 increased the ratelimiting acylation by promoting the leaving group protonation by the adjacent catalytic His. For further details please see Nakagawa et al. pp. 339-346.
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