DEGRADATION OF TETRAHYDROFURFURYL ALCOHOL BY RALSTONIA-EUTROPHA IS INITIATED BY AN INDUCIBLE PYRROLOQUINOLINE QUINONE-DEPENDENT ALCOHOL-DEHYDROGENASE

An organism tentatively identified as Ralstonia eutropha was isolated from enrichment cultures containing tetrahydrofurfuryl alcohol (THFA) as the sole source of carbon and energy. The strain was able to tolera te up to 200 mM THFA in mineral salt medium. The degradation was initi ated by an inducible ferricyanide-dependent alcohol dehydrogenase (ADH ) which was detected in the soluble fraction of cell extracts. The enz yme catalyzed the oxidation of THFA to the corresponding tetrahydrofur an-2-carboxylic acid. Studies with n-pentanol as the substrate reveale d that the corresponding aldehyde was released as a free intermediate. The enzyme was purified 211-fold to apparent homogeneity and could be identified as a quinohemoprotein containing one pyrroloquinoline quin one and one covalently bound heme c per monomer. It was a monomer of 7 3 kDa and had an isoelectric point of 9.1. A broad substrate spectrum was obtained for the enzyme, which converted different primary alcohol s, starting from C-2 compounds, secondary alcohols, diols, polyethylen e glycol 6000, and aldehydes, including formaldehyde. A sequence ident ity of 65% with a quinohemoprotein ADH from Comamonas testosteroni was found by comparing 36 N-terminal amino acids. The ferricyanide-depend ent ADH activity was induced during growth on different alcohols excep t ethanol. In addition to this activity, an NAD-dependent ADH was pres ent depending on the alcohol used as the carbon source.