S.V.Ghodge
et al.
(2013).
Structural and mechanistic characterization of L-histidinol phosphate phosphatase from the polymerase and histidinol phosphatase family of proteins.
Biochemistry,
52,
1101-1112.
PubMed id: 23327428
l-Histidinol phosphate phosphatase (HPP) catalyzes the hydrolysis of
l-histidinol phosphate to l-histidinol and inorganic phosphate, the penultimate
step in the biosynthesis of l-histidine. HPP from the polymerase and histidinol
phosphatase (PHP) family of proteins possesses a trinuclear active site and a
distorted (β/α)(7)-barrel protein fold. This group of enzymes is closely
related to the amidohydrolase superfamily of enzymes. The mechanism of
phosphomonoester bond hydrolysis by the PHP family of HPP enzymes was addressed.
Recombinant HPP from Lactococcus lactis subsp. lactis that was expressed in
Escherichia coli contained a mixture of iron and zinc in the active site and had
a catalytic efficiency of ∼10(3) M(-1) s(-1). Expression of the protein under
iron-free conditions resulted in the production of an enzyme with a 2 order of
magnitude improvement in catalytic efficiency and a mixture of zinc and
manganese in the active site. Solvent isotope and viscosity effects demonstrated
that proton transfer steps and product dissociation steps are not rate-limiting.
X-ray structures of HPP were determined with sulfate, l-histidinol phosphate,
and a complex of l-histidinol and arsenate bound in the active site. These
crystal structures and the catalytic properties of variants were used to
identify the structural elements required for catalysis and substrate
recognition by the HPP family of enzymes within the amidohydrolase superfamily.
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