当前位置： SCI文献检索 > JOURNAL OF INORGANIC BIOCHEMISTRY期刊下所有文献 > Studies of activating and nonactivating metal ion binding to yeast enolase.

Studies of activating and nonactivating metal ion binding to yeast enolase.

Abstract：

:Measurements of binding of certain divalent cations to yeast apoenolase were made using a pH-meter, chromatography, a divalent cation electrode, and ultrafiltration. The binding of the activating metal ions Mg2+ and Co2+ and the nonactivator Ca2+ were studied as functions of the presence or absence of substrate/product, phosphate, and fluoride or level of Tb3+. The data suggest phosphate and fluoride increase Mg2+ binding but not Ca2+ binding. Substrate/product appears to increase Ca2+ binding as well as that of Mg2+ and Co2+. In the presence of substrate, Co2+ binding was 5-6 mol/mol dimer. In the absence of substrate/product, Tb3+ reduced Co2+ binding from 4 mol/mol to 2. These data are interpreted in terms of binding to "conformational," "catalytic" (substrate/product dependent), and "inhibitory" sites. Measurements of Tb3+ fluorescence quenching by Co2+ suggested that the distance between "conformational" sites on the two subunits was large, while the distance between "conformational" and "inhibitory" sites was ca. 17 +/- 4 A. Potentiometric titrations of apoenzyme with Ca2+ and Mg2+ showed that the metal ions produced the same proton release in the presence or absence of substrate/product. If phosphate and fluoride were present, then more protons were released if Ca2+ was the titrant rather than Mg2+, suggesting a difference in ionization state in the complex with the activating metal. Electron paramagnetic resonance studies of Co2+ binding to the various sites in the enzyme are presented. The Co2+ bound to all three sites appears to be high spin, consistent with a preponderance of oxyligands in an octahedral environment. Substrate, citrate, and a strongly binding substrate analogue strongly enhance the hyperfine structure of conformational Co2+. This is interpreted as the result of a change in interaction of an axial ligand to conformational Co2+ produced by carbon-3 of substrate or analogue.

journal_name

J Inorg Biochem

journal_title

Journal of inorganic biochemistry

authors

Brewer JM,Carreira LA,Collins KM,Duvall MC,Cohen C,DerVartanian DV

doi

10.1016/0162-0134(83)85030-2

subject

Has Abstract

pub_date

1983-11-01 00:00:00

pages

255-67

issue

eissn

0162-0134

issn

1873-3344

pii

0162-0134(83)85030-2

journal_volume

pub_type

杂志文章

在线工具

Studies of activating and nonactivating metal ion binding to yeast enolase.