Separation of functionally distinct regions of a macromolecular substrate. Stimulation of tRNA nucleotidyltransferase by a nonreacting fragment of tRNA.

P. Masiakowski, Murray P Deutscher

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Rabbit liver tRNA nucleotidyltransferase catalyzes the incorporation of AMP and CMP into the model acceptor substrate, cytidine. The apparent Km for cytidine in this reaction is about 80 to 90 mM which is more than 10(4) greater than the Km values for the natural substrates, tRNA lacking the terminal AMP (tRNA-C-C) and tRNA lacking the terminal pCpA (tRNA-C). The Vmax values for the model reaction are only 5% and 2% of those for the reaction with the natural tRNA substrates. Addition of the tRNA fragments, tRNA lacking the terminal XpCpCpA sequence (tRNA-(X - 1)p) and tRNA lacking the terminal CpCpA (tRNA-Xp), greatly stimulates the rate of nucleotide incorporation into cytidine. In the case of CMP incorporation into cytidine, tRNA-Xp stimulates the reaction about 60-fold, to a rate similar to that of the normal reaction with tRNA-C. The tRNA fragment has no effect on the apparent Km of either cytidine or CTP, but only alters the Vmax of the reaction. Stimulation of the model reactions is maximal with tRNA fragments of specific chain lengths. These results provide direct evidence that the nonreacting regions of a substrate molecule play an important role in the catalytic efficiency of an enzyme.

Original languageEnglish
Pages (from-to)2585-2587
Number of pages3
JournalJournal of Biological Chemistry
Volume254
Issue number8
StatePublished - Apr 25 1979
Externally publishedYes

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Transfer RNA
Substrates
Cytidine
Cytidine Monophosphate
Adenosine Monophosphate
tRNA nucleotidyltransferase
Cytidine Triphosphate
Chain length
Liver
Nucleotides

ASJC Scopus subject areas

  • Biochemistry

Cite this

Separation of functionally distinct regions of a macromolecular substrate. Stimulation of tRNA nucleotidyltransferase by a nonreacting fragment of tRNA. / Masiakowski, P.; Deutscher, Murray P.

In: Journal of Biological Chemistry, Vol. 254, No. 8, 25.04.1979, p. 2585-2587.

Research output: Contribution to journalArticle

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