Perry Allen Frey

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Ornithine cyclodeaminase catalyzes the conversion of L-ornithine to L-proline by an NAD(+)-dependent hydride transfer reaction that culminates in ammonia elimination. Phylogenetic comparisons of amino acid sequences revealed that the enzyme belongs to the mu-crystallin protein family whose three-dimensional fold has not been reported. Here we describe the(More)
The radical S-adenosylmethionine (SAM) superfamily currently comprises more than 2800 proteins with the amino acid sequence motif CxxxCxxC unaccompanied by a fourth conserved cysteine. The charcteristic three-cysteine motif nucleates a [4Fe-4S] cluster, which binds SAM as a ligand to the unique Fe not ligated to a cysteine residue. The members participate(More)
Galactose-1-phosphate uridylyltransferase catalyzes the reversible transfer of the uridine 5'-monophosphoryl moiety of UDP-glucose to the phosphate group of galactose 1-phosphate to form UDP-galactose. This enzyme participates in the Leloir pathway of galactose metabolism, and its absence is the primary cause of the potentially lethal disease galactosemia.(More)
The biological interconversion of galactose and glucose takes place only by way of the Leloir pathway and requires the three enzymes galactokinase, galactose-1-P uridylyltransferase, and UDP-galactose 4-epimerase. The only biological importance of these enzymes appears to be to provide for the interconversion of galactosyl and glucosyl groups. Galactose(More)
Spectroscopic properties of chymotrypsin and model compounds indicate that a low-barrier hydrogen bond participates in the mechanism of serine protease action. A low-barrier hydrogen bond between N delta 1 of His57 and the beta-carboxyl group of Asp102 in chymotrypsin can facilitate the formation of the tetrahedral adduct, and the nuclear magnetic resonance(More)
Synthesis and overexpression of a gene encoding Escherichia coli UDP-galactose 4-epimerase and engineered to facilitate cassette mutagenesis are described. General acid-base catalysis at the active site of this epimerase has been studied by kinetic and spectroscopic analysis of the wild-type enzyme and its specifically mutated forms Y149F, S124A, S124V, and(More)
UDP-galactose 4-epimerase catalyzes the conversion of UDP-galactose to UDP-glucose through a mechanism involving the transient reduction of NAD+. Here we describe the X-ray structures for epimerase complexed with NADH/UDP, and NAD+/UDP, refined to 1.8 and 2.0 angstrom, respectively. The alpha-carbon positions for the two forms of the enzyme are superimposed(More)
Galactose-1-phosphate uridylyltransferase plays a key role in galactose metabolism by catalyzing the transfer of a uridine 5'-phosphoryl group from UDP-glucose to galactose 1-phosphate. The enzyme from Escherichia coli is composed of two identical subunits. The structures of the enzyme/UDP-glucose and UDP-galactose complexes, in which the catalytic(More)
UDP-galactose 4-epimerase from Escherichia coli catalyzes the interconversion of UDP-glucose and UDP-galactose. In recent years, the enzyme has been the subject of intensive investigation due in part to its ability to facilitate nonstereospecific hydride transfer between beta-NADH and a 4-keto hexopyranose intermediate. The first molecular model of the(More)
UDP-galactose 4-epimerase is one of three enzymes in the metabolic pathway that converts galactose into glucose1-phosphate. Specifically this enzyme catalyzes the interconversion of UDP-galactose and UDP-glucose. The molecular structure of the NADH/UDP-glucose abortive complex of the enzyme from Escherichia coli has been determined by X-ray diffraction(More)