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GTP‐specific pyrophosphorylation of thiamin in dark‐grown soybean ( Glycine max ) seedling axes
Author(s) -
Howle Patrick K. W.,
Fites Roger C.
Publication year - 1991
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1991.tb01707.x
Subject(s) - gtp' , pyrophosphate , glycine , chemistry , nucleotide , seedling , nucleoside , biochemistry , biology , enzyme , amino acid , botany , gene
ATP:thiamin pyrophosphotransferase (TPT: EC 2.7.6.2) was purified 5 900‐fold from 48 h dark‐grown soybean [ Glycine max (L.), Merr. cv. Ransom II] seedling axes. TPT activity was monitored during purification by measuring the formation of thiamin pyrophosphate (TPP) from [2‐ 14 C]‐thiamin at optimal pH (7.3). Although other nucleoside triophosphates were active as pyrophosphate donors (apparent K m s from 21 to 138 m M ), GTP was the preferred nucleotide with an apparent K m of 0.021 m M . TPT activity was extremely sensitive to TPP formation, suggesting product feedback inhibition of TPT activity in vivo. Sulfhydryl, H + and Mg 2+ concentrations, either independently or in concert, were found to affect TPT activity.