Fig. 8
From: Structure-based engineering of heparinase I with improved specific activity for degrading heparin
Structural analysis of Ph-HepI wild-type and mutant enzymes. (a) In the wild-type, Ser169 forms two hydrogen bonds with Leu172 and Glu228. (b) In the mutant S169D, Asp169 forms three hydrogen bonds with adjacent amino acids (Leu172, Glu228, and Asp353) and forms an ionic bond with the calcium ion. (c) In the wild-type, Ala259 forms two hydrogen bonds with Asp257 and Arg261. (d) In the mutant A259D, Asp259 forms three hydrogen bonds with Tyr89, Asp257, and Arg261