A LONG-CHAIN SECONDARY ALCOHOL-DEHYDROGENASE FROM RHODOCOCCUS-ERYTHROPOLIS ATCC-4277

A NAD-dependent secondary alcohol dehydrogenase has been purified from the alkane-degrading bacterium, Rhodococcus erythropolis ATCC 4277. T he enzyme was found to be active against a broad range of substrates, particularly long-chain secondary aliphatic alcohols. Although optimal activity was observed with linear 2-alcohols containing between 6 and 11 carbon atoms, secondary alcohols as long as 2-tetradecanol were ox idized at 25% of the rate seen with mid-range alcohols. The purified e nzyme was specific for the S-(+) stereoisomer of 2-octanol and had a s pecific activity for 2-octanol of over 200 mu mol/min/mg of protein at pH 9 and 37 degrees C, 25-fold higher than that of any previously rep orted S-(+) secondary alcohol dehydrogenase. Linear primary alcohols c ontaining between 3 and 13 carbon atoms were utilized 20- to 40-fold l ess efficiently than the corresponding secondary alcohols. The apparen t K-m value for NAD(+) with 2-octanol as the substrate was 260 mu M, w hereas the apparent K-m values for the 2-alcohols ranged from over 5 m M for 2-pentanol to less than 2 mu M for 2-tetradecanol. The enzyme sh owed moderate thermostability (half-life of 4 h at 60 degrees C) and c ould potentially be useful for the synthesis of optically pure stereoi somers of secondary alcohols.