Schenk, Gerhard and Layfield, Roy and Candy, Judith M. and Duggleby, Ronald G. and Nixon, Peter F.
Molecular Evolutionary Analysis of the Thiamine-Diphosphate-Dependent Enzyme, Transketolase.
Journal of Molecular Evolution , 44.
Members of the transketolase group of thiamine-
diphosphate-dependent enzymes from 17 different
organisms including mammals, yeast, bacteria, and
plants have been used for phylogenetic reconstruction.
Alignment of the amino acid and DNA sequences for 21
transketolase enzymes and one putative transketolase reveals
a number of highly conserved regions and invariant
residues that are of predicted importance for enzyme
activity, based on the crystal structure of yeast transketolase.
One particular sequence of 36 residues has some
similarities to the nucleotide-binding motif and we designate
it as the transketolase motif. We report further
evidence that the recP protein from Streptococcus pneumoniae
might be a transketolase and we list a number of
invariant residues which might be involved in substrate
binding. Phylogenies derived from the nucleotide and the
amino acid sequences by various methods show a conventional
clustering for mammalian, plant, and gramnegative
bacterial transketolases. The branching order of
the gram-positive bacteria could not be inferred reliably.
The formaldehyde transketolase (sometimes known as
dihydroxyacetone synthase) of the yeast Hansenula polymorpha
appears to be orthologous to the mammalian
enzymes but paralogous to the other yeast transketolases.
The occurrence of more than one transketolase gene in
some organisms is consistent with several gene duplications.
The high degree of similarity in functionally important
residues and the fact that the same kinetic mechanism
is applicable to all characterized transketolase
enzymes is consistent with the proposition that they are
all derived from one common ancestral gene. Transketolase
appears to be an ancient enzyme that has evolved
slowly and might serve as a model for a molecular clock,
at least within the mammalian clade.
||Transketolase; Thiamine diphosphate;
Transketolase motif; Evolution; Phylogenetic
trees; Molecular clock;
||Science & Engineering > Chemistry
||07 Jun 2012 15:39
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||Journal of Molecular Evolution
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