Determination of the Number of Regulatory and Catalytic Sites on Aspartate Transcarbamylase

Gordon G. Hammes, Robert W. Porter, Cheng Wen Wu

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Difference spectroscopy and the method of continuous variation have been used to study the stoichiometry of the binding of 5-bromocytidine triphosphate (BrCTP) and of carbamyl phosphate to aspartate transcarbamylase. The regulatory subunit binds 1 equiv of BrCTP to a protein equivalent molecular weight of 17,000, and native aspartate transcarbamylase binds 6 equiv to a protein equivalent molecular weight of 310,000. The catalytic subunit binds three equivalents of the substrate, carbamyl phosphate, per catalytic subunit of mol wt 100, 000. Since native aspartate transcarbamylase has two catalytic subunits and a molecular weight of 310,000, these data suggest that the enzyme has six regulatory and six catalytic sites.

Original languageEnglish
Pages (from-to)2992-2994
Number of pages3
JournalBiochemistry
Volume9
Issue number15
DOIs
StatePublished - 1 Jul 1970

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