Emodin O-methyltransferase fromAspergillus terreus
✍ Scribed by Zhi-Gang Chen; Isao Fujii; Yutaka Ebizuka; Ushio Sankawa
- Book ID
- 104681285
- Publisher
- Springer
- Year
- 1992
- Tongue
- English
- Weight
- 610 KB
- Volume
- 158
- Category
- Article
- ISSN
- 0302-8933
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✦ Synopsis
Emodin O-methyltransferase, an enzyme catalyzing methylation of the 8-hydroxy group of emodin, was identified in the mould Aspergillus terreus IMI 16043, a (+)-geodin producing strain. The enzyme catalyzed the formation of questin from emodin and S-adenosyl-L-methionine. By chromatography on DEAE-cellulose, Phenyl Sepharose, Q-Sepharose, Hydroxyapatite, and CM-cellulose, emodin O-methyltransferase was purified to apparent homogeneity. The purified protein had a molecular weight of 322 kDa as estimated by gel filtration and 53.6 kDa as estimated by gel electrophoresis under denaturing conditions, suggesting that the active enzyme was a homohexamer. The enzyme showed pI 4.4 and optimum pH 7-8. Magnesium ion or manganese ion was not an absolute requirement, nor increased the enzyme activity. The enzyme had strict substrate specificity and very low Km values for both emodin (3.4 x 10(-7) M) and S-adenosyl-L-methionine (4.1 x 10(-6) M).