COMPLETE ANAEROBIC OXIDATION OF HYDROQUINONE BY DESULFOCOCCUS SP STRAIN HY5 - INDICATIONS OF HYDROQUINONE CARBOXYLATION TO GENTISATE

The sulfate-reducing strain Hy5 was able to grow with hydroquinone as sole source of carbon and energy. In experiments with dense cell suspe nsions, several indications were found that gentisate was the first in termediate in anaerobic degradation of hydroquinone: (1) degradation o f hydroquinone was accelerated by addition of bicarbonate; (2) cell su spensions grown with hydroquinone oxidized gentisate at a rate similar to that of suspensions grown with gentisate, whereas the latter were not able to degrade hydroquinone in the presence of chloramphenicol; ( 3) in SDS-PAGE analysis of cell-free extracts of strain Hy5, two addit ional protein bands were found after growth with hydroquinone that wer e not detected in cells grown with gentisate, probably representing a hydroquinone carboxylating enzyme. A corresponding enzyme activity cou ld not be detected. In cell-free extracts of hydroquinone-grown strain Hy5, the specific acyl-CoA ligase activity with gentisate as substrat e was detected at 70 nmol x mg(-1) x min(-1). Gentisyl-CoA was enzymat ically reduced to several unidentified nonaromatic products in the pre sence of dithionite-reduced methyl viologen.