Development of the regio- and stereospecific proline hydroxylases and their application

Abstract

This article describes microbial proline hydroxylases which carry out regio- and stereospecific hydroxylation of free L-proline and their application to the enzymatic synthesis of hydroxyprolines and related compounds. Proline 4-hydroxylase activities were detected in 8 actinomycetes strains, and proline 3-hydroxylase activities were detected in 3 actinomycetes and 2 Bacillus strains. Both enzymes were purified and characterized. The enzymes required 2-oxoglutarate and Fe2+ for the reaction. Proline 4-hydroxylase hydroxylated L-proline in a regio- and stereospecific manner at C-4 to form trans-4-hydroxy-L-proline, while 3-hydroxylase hydroxylated C-3 of L-proline to form cis-3-hydroxy-Lproline. Efficient biotransformation systems of L-proline to trans-4-hydroxy-L-proline or cis-3-hydroxy-L-proline were established using recombinant DNA technology. Both of the enzymes hydroxylated L-2-azetidine carboxylate, 3,4-dehydro-L-proline and L-pipecolate in a regio- and stereospecific manner, however, D-proline, N-substituted L-proline, L-proline ester and peptidyl L-proline do not react as substrates for either 4- or 3-hydroxylases.