On the Cofactor Specificity of Glycinamide Ribonucleotide and 5-Aminoimidazole-4-carboxamide Ribonucleotide Transformylase from Chicken Liver

Gary K. Smith, W. Thomas Mueller, Patricia A. Benkovic, Stephen J. Benkovic

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61 Scopus citations

Abstract

Tests of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and glycinamide ribonucleotide (GAR) transformylase cofactor specificity were conducted with 5- and/or 8-deazafolate analogues formylated at N-10. Several of these compounds were found to serve as cofactors for both the enzymes. The finding that 10-formyl-8-deazafolate can be used by AICAR transformylase eliminates those mechanisms requiring cyclization to a methenyl derivative prior to carbon unit transfer for this transformylase. Surprisingly, a similar analogue, 10-formyl-5,8-deazafolate, is very effective as a cofactor for GAR transformylase in the presence or absence of the trifunctional protein which is required for 5,10- methenyl-H4-folate activity with this transformylase. This finding suggests that the trifunctional protein modulates GAR transformylase cofactor specificity by supplying the active cofactor as the iV10-formyl species, possibly through a transport process that avoids its dissociation into solution.

Original languageEnglish (US)
Pages (from-to)1241-1245
Number of pages5
JournalBiochemistry
Volume20
Issue number5
DOIs
StatePublished - Mar 1981

All Science Journal Classification (ASJC) codes

  • Biochemistry

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