SITE-DIRECTED MUTAGENESIS OF THE CONSERVED SERINE-138 OF HUMAN PLACENTAL NAD(-DEPENDENT 15-HYDROXYPROSTAGLANDIN DEHYDROGENASE TO AN ALANINERESULTS IN AN INACTIVE ENZYME())

Human placental NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH) is a member of the short-chain dehydrogenase family of enzy mes. It has been proposed that a highly conserved serine residue (corr esponding to serine 138 of 15-PGDH) may be involved in the catalytic m echanism of many of these enzymes. Site-directed mutagenesis was used to change serine 138 of NAD(+)-dependent 15-hydroxy-prostaglandin dehy drogenase to an alanine. The mutant protein was then expressed in E. c oli. Western blot analysis indicated that the S138A mutant protein was expressed at levels similar to the wild type enzyme; however, the mut ant protein was found to be inactive. These results support the propos ed role of this highly conserved serine in enzyme activity. (C) 1990 A cademic Press, Inc.