Purification and characterization of the short-chain alkylsulphatase of coryneform B1a

Abstract

Using a combination of streptomycin sulphate precipitation, and DEAE-cellulose and butyl-agarose chromatography, an alkylsulphatase active towards short-chain alkyl sulphates has been purified approx. 70-fold from extracts of coryneform B1a grown on butyl-1-sulphate. The enzyme protein is dimeric with a subunit molecular mass of 77.6 kDa, has an isoelectric point of pI 7.2, and converts butyl-1-sulphate stoichiometrically into butan-1-ol and inorganic sulphate. Stoichiometric incorporation of 18O from H218O into sulphate during the reaction showed that enzymic hydrolysis occurred at the O-S bond of the C-O-S ester linkage. The enzyme was active on C3-C7 linear primary alkyl sulphates but not on higher (C8,9) or lower (C1,2) homologues, although the latter pair were competitive inhibitors. The specificity constant (k(cat.)/K(m)) was highest for pentyl sulphate (K(m) 1.89±0.38 mM; k(cat.) 6.86±0.52 s-1) and decreased for higher and lower homologues. No activity was detected towards C3-C9 racemic alkyl-2-sulphates, D- or L-enantiomers of butyl-2-sulphate, the symmetrical secondary alkyl sulphates pentyl-3-sulphate, heptyl-4-sulphate, nonyl-5-sulphate, C1-C8 alkane sulphonates, choline sulphate, or butyric acid-4-sulphate; none of these compounds (except the symmetrical esters and butyric acid-4-sulphate, which were not tested) was demonstrably inhibitory. The enzyme was compared with other alkylsulphatases in terms of substrate specificity and mode of action.