Premium
A gene duplication led to specialized γ‐aminobutyrate and β‐alanine aminotransferase in yeast
Author(s) -
Andersen Gorm,
Andersen Birgit,
Dobritzsch Doreen,
Schnackerz Klaus D.,
Piškur Jure
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.05729.x
Subject(s) - gene duplication , yeast , alanine aminotransferase , gene , alanine , genetics , biochemistry , chemistry , biology , endocrinology , amino acid
In humans, β‐alanine (BAL) and the neurotransmitter γ‐aminobutyrate (GABA) are transaminated by a single aminotransferase enzyme. Apparently, yeast originally also had a single enzyme, but the corresponding gene was duplicated in the Saccharomyces kluyveri lineage. Sk UGA1 encodes a homologue of Saccharomyces cerevisiae GABA aminotransferase, and Sk PYD4 encodes an enzyme involved in both BAL and GABA transamination. Sk PYD4 and Sk UGA1 as well as S. cerevisiae UGA1 and Schizosaccharomyces pombe UGA1 were subcloned, over‐expressed and purified. One discontinuous and two continuous coupled assays were used to characterize the substrate specificity and kinetic parameters of the four enzymes. It was found that the cofactor pyridoxal 5′‐phosphate is needed for enzymatic activity and α‐ketoglutarate, and not pyruvate, as the amino group acceptor. SkPyd4p preferentially uses BAL as the amino group donor ( V max / K m = 0.78 U·mg −1 ·m m −1 ), but can also use GABA ( V max / K m = 0.42 U·mg −1 ·m m −1 ), while SkUga1p only uses GABA ( V max / K m = 4.01 U·mg −1 ·m m −1 ). SpUga1p and ScUga1p transaminate only GABA and not BAL. While mammals degrade BAL and GABA with only one enzyme, but in different tissues, S. kluyveri and related yeasts have two different genes/enzymes to apparently ‘distinguish’ between the two reactions in a single cell. It is likely that upon duplication ∼200 million years ago, a specialized Uga1p evolved into a ‘novel’ transaminase enzyme with broader substrate specificity.