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P 1 , P 3 ‐bis(5′‐adenosyl)triphosphate (Ap 3 A) as a substrate and a product of mammalian tryptophanyl‐tRNA synthetase
Author(s) -
Merkulova Tatyana,
Kovaleva Galina,
Kisselev Lev
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00764-0
Subject(s) - adenylate kinase , substrate (aquarium) , enzyme , transfer rna , chemistry , aminoacyl trna synthetase , adenosine triphosphate , stereochemistry , biochemistry , nucleotide , biology , rna , ecology , gene
Bovine tryptophanyl‐tRNA synthetase (TrpRS, E.C. 6.1.1.2) is unable to catalyze in vitro formation of Ap 4 A in contrast to some other aminoacyl‐tRNA synthetases. However, in the presence of l ‐tryptophan, ATP‐Mg 2+ and ADP the enzyme catalyzes the Ap 3 A synthesis via adenylate intermediate. Ap 3 A (not Ap 4 A) may serve as a substrate for TrpRS in the reaction of E·(Trp ∼ AMP) formation and in the tRNA Trp charging. The K m value for Ap 3 A was higher than the K m for ATP (approx. 1.00 vs. 0.22 mM) and V max was 3 times lower than for ATP. The Zn 2+ ‐deficient enzyme catalyzes Ap 3 A synthesis in the absence of exogenous ADP due to ATPase activity of Zn 2+ ‐deprived TrpRS. The inability of mammalian TrpRS to synthesize Ap 4 A, might be considered as a molecular tool preventing the removal of Zn 2+ due to chelation by Ap 4 A and therefore preserving the enzyme activity.