ISSN:
1432-072X
Keywords:
O-methyltransferase
;
Aspergillus terreus
;
Emodin
;
Questin
;
S-Adenosyl-l-methionine
;
Purification
;
Molecular weight
;
Isoelectric point
;
Steady-state kinetics
;
Substrate specificity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract 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 (3.4×10-7 M) and S-adenosyl-l-methionine (4.1×10-6 M).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00249062
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