Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus.

Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Research Abstract Details 

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Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Abstract Text:

S Fujii,B Inoue,H Yamamoto,K Ogata,T Shinki,S Inoue,M Tomita,H Tamura,K Tsukamoto,H Ikezawa,K Ikeda,

The modes of Mg2+ binding to SMase from Bacillus cereus were studied on the basis of the changes in the tryptophyl fluorescence intensity. This enzyme was shown to possess at least two binding sites for Mg2+ with low and high affinities. The effects of Mg2+ binding on the enzymatic activity and structural stability of the enzyme molecule were also studied. The results indicated that the binding of Mg2+ to the low-affinity site was essential for the catalysis, but was independent of the substrate binding to the enzyme. It was also indicated that the alkaline denaturation of the enzyme was partly prevented by the Mg2+ binding, whereas no significant protective effect was observed against the denaturation by urea. The pH dependence of the kinetic parameters for the hydrolysis of micellar HNP and mixed micellar SM with Triton X-100 (1:10), catalyzed by SMase from B. cereus, was studied in the presence of a large amount of Mg2+ to saturate both the low- and high-affinity sites. The pH dependence curves of the logarithm of 1/Km for these two kinds of substrates were similar in shape to each other, and showed a single transition. On the other hand, the shapes of the pH dependence curves of the logarithm of kcat for these two kinds of substrates were different from each other. The pH dependence curve for micellar HNP showed three transitions and, counting from the acidic end of the pH region, the first and third transitions having tangent lines with slopes of +1 and -1, respectively. On the other hand, the curve for mixed micellar SM with Triton X-100 showed one large transition with a slope of +1 (the first transition) and a very small transition (the third transition). On the basis of the present results and the three-dimensional structure of bovine pancreatic DNase I, which has a primary structure similar to that of B. cereus SMase, we proposed a catalytic mechanism for B. cereus SMase based on general-base catalysis.

Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Publishing Authors By Initials

S Fujii,B Inoue,H Yamamoto,K Ogata,T Shinki,S Inoue,M Tomita,H Tamura,K Tsukamoto,H Ikezawa,K Ikeda,

For similar organic chemicals: urea research abstracts see: organic chemicals: urea research

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Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Journal Published:

PUBLICATION TYPE: Research Support, Non-U.S. Gov

Journal: Journal of biochemistry

VOLUME: 124

Page Numbers: 1178-87

Journal Abbreviation: J. Biochem.

ISSN: 0021-924X

DAY: 1

MONTH: Dec

YEAR: 1998

Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Information

Number of References:

LANGUAGE: eng

NlmUniqueID: 376600

Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Keywords Mesh Terms:

KEYWORDS: Urea

MESH TERMS: chemistry

Chemical & Substance for Abstract: Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus. Information

Substance Name: Sphingomyelin Phosphodiesterase

Registry Number: EC 3.1.4.12

Grant and Affiliation Information for Mg2+ binding and catalytic function of sphingomyelinase from Bacillus cereus.

AFFILIATION: Department of Biochemistry, Osaka University of Pharmaceutical Sciences, Takatsuki, Osaka, 569-1094, Japan.

Country: JAPAN

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MEDLINETA: J Biochem

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