title: Biosynthesis of hydroxymethylpyrimidine pyrophosphate in Saccharomyces cerevisiae.
abstract: Two redundant genes, THI20 and THI21, of Saccharomyces cerevisiae encode a 2-methyl-4-amino-5-hydroxymethylpyrimidine monophosphate (HMP-P) kinase required for thiamin biosynthesis. Using functional complementation analysis with an Escherichia coli mutant strain and a defined biochemical system containing partially purified proteins for the reconstitution of thiamin monophosphate synthesis, we demonstrate that both Thi20p and Thi21p proteins also have HMP kinase activity. Although each isoform independently can synthesize HMP pyrophosphate (HMP-PP) from HMP, there is a marked difference in efficiency between the two proteins. The thi20 deletion strain grows at the same rate as the parental strain in minimal medium without thiamin, but its ability to synthesize HMP-PP from HMP is significantly decreased. We discuss the possibility that HMP is not involved in the pathway of de novo thiamin synthesis in S. cerevisiae.
authors.affiliation: Department of Food Microbiology, Doshisha Women's College, Kamigyo-ku, Kyoto 602-0893, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Kawasaki
authors.forename: Mari
authors.initials: M
authors.lastname: Onozuka
authors.forename: Tomoko
authors.initials: T
authors.lastname: Mizote
authors.forename: Kazuto
authors.initials: K
authors.lastname: Nosaka
mesh_terms: D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D011743:Pyrimidines / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D013835:Thiamine Pyrophosphate / Q000096:biosynthesis*
chemical_list: D011743:Pyrimidines; D029701:Saccharomyces cerevisiae Proteins; C108436:4-amino-5-(hydroxymethyl)-2-methylpyrimidine phosphate kinase; D017856:Phosphotransferases (Phosphate Group Acceptor); D013835:Thiamine Pyrophosphate