Catalytic properties and specificity of phosphoserine aminotransferase from beef liver

Basurko, Marie-Jose; Marche, Michèle; Darriet, M.; Cassaigne, André

doi:10.1042/bst0170787

Cited by 5 publications

(4 citation statements)

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“…These experiments conducted with various xed a KG concentrations also allowed the determination of the a KG inhibition constant value. Moreover, these kinetic inhibition patterns con rm the ping-pong mechanism previously evidenced (14). The K m and K i values for the four reactants of the PSerAT-catalyzed reaction are summarized in Table 1.…”

Section: Kinetic Propertiessupporting

confidence: 82%

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Phosphoserine Aminotransferase, the Second Step-Catalyzing Enzyme for Serine Biosynthesis

Basurko¹,

Marche²,

Darriet³

et al. 1999

IUBMB: Life

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As a step toward analyzing the serine biosynthetic pathway in mammals, we have studied the properties of phosphoserine aminotransferase, the second step-catalyzing enzyme. The K(m) values for 3-phosphohydroxypyruvate and L-phosphoserine are 5 and 35 microM, respectively, and those for glutamate and alpha-ketoglutarate are 1.2 and 0.8 mM, respectively. The product inhibition studies strengthened the support for a ping-pong mechanism and allowed evaluation of Ki values for the four substrates. The equilibrium constant evaluated from the kinetic parameters is approximately 40. Additionally, some physical properties relative to the bound coenzyme and the secondary structure were investigated. The results are consistent with a structural relationship between the Escherichia coli enzyme and the mammalian enzyme. The mammalian enzyme has specific kinetic parameters, the determination of which is a prerequisite to analyzing the serine biosynthetic pathway in mammals.

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Section: Kinetic Propertiessupporting

confidence: 82%

“…Then, a homodimeric structure with a 43-kDa subunit molecular mass was determined for the beef liver enzyme (13). Concerning the kinetic properties, we have previously reported (14) kinetic data supporting a ping-pong bi-bi mechanism and the K m values of the substrates involved in the forward direction.…”

Section: Introductionmentioning

confidence: 98%

Phosphoserine Aminotransferase, the Second Step-Catalyzing Enzyme for Serine Biosynthesis

Basurko¹,

Marche²,

Darriet³

et al. 1999

IUBMB: Life

Self Cite

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“…The catalytic mechanism and the functional parameters were defined for several PSATs from eukaryotes and bacteria (Ali & Nozaki, 2006; Basurko et al, 1989; Basurko et al, 1999; Fell & Snell, 1988; Haque et al, 2019; Hirsch & Greenberg, 1967; Koivulehto et al, 2020; Singh et al, 2019; Snell & Fell, 1990), but this information is lacking for the human enzyme (Baek et al, 2003; Donini et al, 2009). In analogy to aspartate transaminase and other PLP‐dependent aminotransferases, PSAT follows a ping–pong mechanism, with L‐glutamate (L‐Glu) binding first (Basurko et al, 1989). This half‐reaction leads to the formation of pyridoxamine phosphate (PMP), which subsequently reacts with the second substrate, 3‐PHP, to form OPS and regenerate the PLP internal aldimine (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

“…The only complete characterization of a mammalian PSAT available to date was published by Basurko and collaborators on the enzyme purified from bovine liver (Basurko et al, 1989; Basurko et al, 1999). Furthermore, very little is known about the enzyme regulation by physiologically relevant metabolites, with many studies focusing on the reactivity towards amino acid substrates.…”

Section: Introductionmentioning

confidence: 99%

L‐serine biosynthesis in the human central nervous system: Structure and function of phosphoserine aminotransferase

et al. 2023

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Organisms from all kingdoms of life synthesize L‐serine (L‐Ser) from 3‐phosphoglycerate through the phosphorylated pathway, a three‐step diversion of glycolysis. Phosphoserine aminotransferase (PSAT) catalyzes the intermediate step, the pyridoxal 5′‐phosphate‐dependent transamination of 3‐phosphohydroxypyruvate and L‐glutamate to O‐phosphoserine (OPS) and α‐ketoglutarate. PSAT is particularly relevant in the central nervous system of mammals because L‐Ser is the metabolic precursor of D‐serine, cysteine, phospholipids, and nucleotides. Several mutations in the human psat gene have been linked to serine deficiency disorders, characterized by severe neurological symptoms. Furthermore, PSAT is overexpressed in many tumors and this overexpression has been associated with poor clinical outcomes. Here, we report the detailed functional and structural characterization of the recombinant human PSAT. The reaction catalyzed by PSAT is reversible, with an equilibrium constant of about 10, and the enzyme is very efficient, with a kcat/Km of 5.9 × 106 M−1 s−1, thus contributing in driving the pathway towards the products despite the extremely unfavorable first step catalyzed by 3‐phosphoglycerate dehydrogenase. The 3D X‐ray crystal structure of PSAT was solved in the substrate‐free as well as in the OPS‐bound forms. Both structures contain eight protein molecules in the asymmetric unit, arranged in four dimers, with a bound cofactor in each subunit. In the substrate‐free form, the active site of PSAT contains a sulfate ion that, in the substrate‐bound form, is replaced by the phosphate group of OPS. Interestingly, fast crystal soaking used to produce the substrate‐bound form allowed the trapping of different intermediates along the catalytic cycle.

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Crystal structure of phosphoserine aminotransferase from Escherichia coli at 2.3 Å resolution: comparison of the unligated enzyme and a complex with α-methyl- l -glutamate 1 1Edited by R. Huber

Hester

Stark

Moser

et al. 1999

Journal of Molecular Biology

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Catalytic properties and specificity of phosphoserine aminotransferase from beef liver

Cited by 5 publications

References 1 publication

Phosphoserine Aminotransferase, the Second Step-Catalyzing Enzyme for Serine Biosynthesis

Phosphoserine Aminotransferase, the Second Step-Catalyzing Enzyme for Serine Biosynthesis

L‐serine biosynthesis in the human central nervous system: Structure and function of phosphoserine aminotransferase

Crystal structure of phosphoserine aminotransferase from Escherichia coli at 2.3 Å resolution: comparison of the unligated enzyme and a complex with α-methyl- l -glutamate 1 1Edited by R. Huber

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