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J. Biochem, 1988, Vol. 103, No. 5 878-883
© 1988 Japanese Biochemical Society

research-article

A Novel Anthraquinone Ring Cleavage Enzyme from Aspergillus terreus

Isao Fujii, Yutaka Ebizuka and Ushio Sankawa1

Faculty of Pharmaceutical Sciences, The University of Tokyo Bunkyo-ku, Tokyo 113

1To whom correspondence should be addressed.

An enzyme activity which catalyzes the ring cleavage of the anthraquinone questin to form benzophenone desmethylsulochrin was found in the cell-free extract of Aspergillus terreus, a (+)-geodin producer. The product was identified as desmethylsulochrin by high-resolution mass spectroscopy and chemical carrier dilution analysis. The enzyme showed an absolute requirement of NADPH and molecular oxygen. Therefore, the enzyme, named questin oxygenase, was considered to be classified as a monooxygenase. The optimum pH was around 7.5. The enzyme was very unstable and lost its activity completely after storage overnight at 4°C in 0.05 M phosphate buffer, pH 7.5. The instability of the questin oxygenase was partially overcome by the addition of polyols and the non-ionic detergent Tween 80 to the buffer. By DEAE-cellulose column chromatography, two protein fractions, named DE-1 and DE-II, were obtained. Neither fraction reacted with questin by itself. However, the combination of DE-I and DE-II reconstituted the questin oxygenase system to convert questin to desmethylsulochrin. This result suggested that the system is not a simple combination of oxygenase and hydrolase, but requires some additional fator(s) such as electron transfer protein.


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