AMP and IMP dephosphorylation by soluble high- and low-Km 5'-nucleotidases

Spychała, Józef; Madrid‐Marina, Vicente; Nowak, Paul J.; Fox, I. H.

doi:10.1152/ajpendo.1989.256.3.e386

Cited by 10 publications

(9 citation statements)

References 16 publications

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“…Since soluble cellular extracts contain additional phosphatases as well as kinases (e.g. Truong et al, 1988;Spychala et al, 1989;Yamazaki et al, 1991) the physiological interpretation of the kinetic data obtained has yet to be viewed with some reservation.…”

Section: Plant 5'-nucleotidasementioning

confidence: 99%

5′-Nucleotidase: molecular structure and functional aspects

Zimmermann

1992

Biochemical Journal

802

701

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Section: Plant 5'-nucleotidasementioning

confidence: 99%

5′-Nucleotidase: molecular structure and functional aspects

Zimmermann

1992

Biochemical Journal

802

701

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“…Enzymes in this family catalyze hydrolysis of phosphate from diverse substrates including polypeptides, sphingomyelin, RNA, DNA and nucleotides. [19][20][21][22] Monoclonal antibodies and quantitative real time-PCR have been used to determine CD73 distribution. The active site resides between the two domains.…”

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confidence: 99%

5′-Nucleotidases and their new roles in NAD+ and phosphate metabolism

Bogan

Brenner

2010

New J. Chem.

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5 0 -Nucleotidase (EC 3.1.3.5) designates a set of enzymes, which catalyze the hydrolysis of ribonucleoside and deoxyribonucleoside monophosphates into the corresponding nucleosides plus orthophosphate. 5 0 -Nucleotidases are classified according to subcellular localization, nucleobase specificity and their ability to hydrolyze deoxynucleoside monophosphate substrates. Membrane-bound 5 0 -nucleotidases are ectoenzymes principally involved in salvage of extracellular nucleosides, and often display a preference toward adenosine monophosphate, thereby modulating signal transduction cascades involving purinergic receptors. Cytosolic 5 0 -nucleotidases are members of the haloacid dehalogenase superfamily of enzymes, which are two-domain proteins containing a modified Rossman fold as the core and a variable cap structure. Extracellular and intracellular 5 0 -nucleotidase activities participate in purine and pyrimidine salvage to support balanced synthesis of nucleotides, which is critical for maintaining high fidelity DNA replication. While the production of ribonucleosides from ribonucleotides by 5 0 -nucleotidases remains the most well studied function, it appears that the physiological functions of these activities are more broad. Indeed, Sdt1, previously termed a pyrimidine-specific 5 0 -nucleotidase, and Isn1, previously termed an inosine monophosphate (IMP)-specific 5 0 -nucleotidase, have recently been implicated in catabolic processes in nicotinamide adenine dinucleotide (NAD + ) metabolism, and are regulated by the NAD + precursor vitamin nicotinic acid, glucose and phosphate availability in the medium. In addition, Usha, Pho5, Sdt1 and Phm8 are phosphate starvation-induced 5 0 -nucleotidases with diverse substrate specificities that liberate phosphate under phosphate starvation conditions. Here we review 5 0 -nucleotidase enzyme structure, catalytic mechanism and substrate specificity and focus on new biological roles for these enzymes in nucleotide, NAD + and phosphate metabolism. 5 0 -Nucleotidases are regulators of nucleotide and nucleobase metabolism 5 0 -Nucleotidase was first reported to dephosphorylate AMP and IMP in heart and skeletal muscle. 1 Since this discovery, similar enzymes have been described in diverse species, tissues

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“…The 5'-phosphomonoesterase activity is a composite of nonspecific phosphatases and specific 5'nucleotidases. There are two soluble specific 5'nucleotidases in lymphoid tissue: low Km and high Km forms [24]. Our previous studies determined that the decrease in 5'-nucleotidase in T-lymphoblasts is apparently related to the low Km form [24].…”

Section: Introductionmentioning

confidence: 98%

“…There are two soluble specific 5'nucleotidases in lymphoid tissue: low Km and high Km forms [24]. Our previous studies determined that the decrease in 5'-nucleotidase in T-lymphoblasts is apparently related to the low Km form [24]. Therefore, as one approach to examine the decreased nucleoside 5'-monophosphate activity of these cells, we have tested the hypothesis that there is an alteration of specific soluble low Km 5'-nucleotidase in Tlymphoblasts as compared to B-lymphoblasts.…”

Section: Introductionmentioning

confidence: 99%

Altered properties of human t-lymphoblast soluble low Km 5′-nucleotidase: Comparison with B-lymphoblast enzyme

Madrid‐Marina¹,

Lestan²,

Nowak³

et al. 1993

Leukemia Research

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Soluble low Km 5'-nucleotidases have been purified from human cultured T- and B-lymphoblasts to compare their properties and to examine the mechanism of different rates of nucleotide dephosphorylation. The enzyme from B-lymphoblasts (MGL-8) was 4385-fold purified with a specific activity of 114 mumol/min/mg, while the enzyme from T-lymphoblasts (CEM, MOLT-4) was 4355-fold purified with a specific activity of 35 mumol/min/mg. The activity of both enzymes have an absolute requirement for Mg++. The B-cell enzyme has maximum activity with Mg2+ > Mn2+ > Co2+, while the T-cell enzyme had maximum activity with Co2+ > Mn2+ > Mg2+. The optimum activity was at pH 7.4-9.0 for the B-cell enzyme and pH 9.0 for the T-cell enzyme. Substrate specificity was the same for both enzymes with the following relative Vmax values: CMP > UMP > dUMP > dCMP > dAMP > IMP > GMP > dIMP > dGMP. The Km values for AMP and IMP were 12 and 25 microM for the B-cell enzyme, and 7.0 and 12 microM for the T-cell enzyme. ATP and ADP are competitive inhibitors of these enzymes with apparent Ki values of 100 and 20 microM for the B-cell enzyme, and 44 microM and 8 microM for the T-cell enzyme, respectively. The apparent molecular mass by gel filtration column chromatography is 145 kD for the B-cell enzyme and 72 kDa for the T-cell enzyme. The subunit molecular masses by Western blots are 69.2 kD for both enzymes. These properties suggest that the B-lymphoblast enzyme is identical or similar to the enzyme from human placenta. However, the T-cell enzyme has some different properties. We conclude that these differences plus a lower content of low Km 5'-nucleotidase in T-cells may account for the decreased ability of T-lymphoblasts to dephosphorylate nucleotides and may contribute to the selective cytotoxicity of deoxyribonucleosides for T-lymphoblasts as compared to B-lymphoblasts.

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AMP and IMP dephosphorylation by soluble high- and low-Km 5'-nucleotidases

Cited by 10 publications

References 16 publications

5′-Nucleotidase: molecular structure and functional aspects

5′-Nucleotidase: molecular structure and functional aspects

5′-Nucleotidases and their new roles in NAD+ and phosphate metabolism

Altered properties of human t-lymphoblast soluble low Km 5′-nucleotidase: Comparison with B-lymphoblast enzyme

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