HNL from Linum usitatissimum

ImHNL is a nonglycosylated homodimer (84 kDa) which catalyzes the reversible cleavage of aliphatic (R)-cyanohydrins [34]. This HNL does not require complex protein modification after protein biosynthesis. Thus, expression in prokaryotic Escherichia coli) and eukaryotic hosts Pichia pastoris) is possible [35-37]. However, initial trials to express IwHNL in E. coli were hampered by formation of inclusion bodies [36]. 

Homology model and putative active center Using the program SWISS Model a homology model of IwHNL was created using the 3D structures of similar en- 

The authors thank the Deutsche Forschungsgemeinschaft (DFG) for financial support in the SFB 380. We gratefully acknowledge our cooperation partners M. Muller, A. Liese, and C. Wandrey for fruitful discussions and H. Wajant for providing the SfeHNL clone. 

Protein design on pyruvate decarboxylase (PDC) by site-directed mutagenesis. Application to mechanistical investigations, and tailoring PDC for the use in organic synthesis. Adv. Biochem. Eng. BioUchnol. 1997, 58, 15-43. 

Dohritzsch, S. Konig, G. Schneider, G. Lu, High resolution crystal structure of pyruvate decarboxylase from Zymomonas mohilis. Implications for substrate activation in pyruvate decarboxylases. J. Biol. Chem. 1998, 273, 20 196-20 204. 

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As described in Sec. III.A, PaHNL from bitter almonds is an excellent biocatalyst for the preparation of (.R)-cyanohydrins. Since the functional overexpression of PaHNL was not successful so far and some substrates, e.g., acrolein, gave only low optical yields, the catalytic suitability of the (J )-specific HNL from Linum usitatissimum [30] for the preparation of (/ )-cyanohydiins was recently investigated [31]. The HNL from L. usitatissimum has been cloned and overexpressed in P. pastoris giving convenient access to recombinant enzyme for synthetic plications [31]. In Table 10 the LuHNL-catalyzed addition of HCN to alddiydes and ketones yielding the corresponding (P)-cyanohydrins is summarized [31b]. 

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