X-RAY STRUCTURE ANALYSIS OF ALDEHYDE REDUCTASE FROM A RED YEAST. A. Kita¹⁾, M. Kataoka²⁾, K. Yamamoto²⁾, S. Shimizu²⁾, K. Kita³⁾, T. Hashimoto³⁾, H. Yamane³⁾, K. Miki¹⁾, ¹⁾Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan, ²⁾Department of Agricultural Chemistry, Faculty of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan, ³⁾Department of Biotechnology, Faculty of Engineering, Tottori University, Tottori 680, Japan

We crystallized aldehyde reductase from S. salmonicolor for X-ray structure analysis. There is a class of monomeric NADH-dependent oxidoreductases with molecular masses about 35,000 which is called the aldo-keto reductase superfamily. Aldehyde reductase of Sporobolomyces salmonicolor well catalyzes not only the NADH-dependent reduction of p-nitrobenzaldehyde and pyridine-3-aldehyde, which were typical substrates for mammalian aldehyde and aldose reductases, but also that of prochiral carbonyl compounds such as 4-chloro-3-oxobutanoate esters. Since the later products are optically active alcohols, the enzyme could recognize the stereo-position of these substrates. This stereoselectivity might be dependent on the tertiary structure of the enzyme, therefore elucidation of the tertiary structure of aldehyde reductase is significant for elucidation of mechanism controlling stereoselectivity.

Hexagonal crystals were obtained from ammonium sulfate solution by vapor diffusion (M. Kataoka, et al., Acta Cryst., in press). The space group is P6₁22 or P6₅22 with unit cell dimensions of a=b=72.2Å, c=320Å. Assuming two molecules are in the asymmetric unit, V_m is calculated to be 1.7ų/Da. Intensity data were collected on a Weissenberg camera with synchrotron radiation at BL-6A₂ at the Photon Factory, KEK, Japan. Intensities were processed and scaled up to 2.2Å resolution. The Rmerge is 5.9% for 18535 independents on the native crystal. The structure analysis is in progress.