Wyniki wyszukiwania - Biblioteka Nauki

1

Specific and nonspecific enzymes involved in the catabolism of minor mono- and dinucleoside polyphosphates

100%

Guranowski A.

Cellular and Molecular Biology Letters

|

1999

|

tom 04

|

nr 3

2

Analogs of diadenosine tetraphosphate [Ap4A]

100%

Guranowski A.

|

nr 4

EN

This review summarizes our knowledge of analogs and derivatives of diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A), the most extensively studied member of the dinucleoside 5',5"'-P1,Pn-polyphosphate (NpnN) family. After a short discussion of enzymes that may be responsible for the accumulation and degradation of Np4N's in the cell, this review focuses on chemically and/or enzymatically produced analogs and their practical applications. Particular attention is paid to compounds that have aided the study of enzymes involved in the metabolism of Ap4A (Np4N'). Certain Ap4A analogs were alternative substrates of Ap4A-degrading enzymes and/or acted as enzyme inhibitors, some other helped to establish enzyme mechanisms, increased the sensitivity of certain enzyme assays or produced stable enzyme:ligand complexes for structural analysis.

3

O adenozyno-5'-tetrafosforanie

63%

Guranowski A. , Pietrowska-Borek M.

|

nr 3

4

Selective splitting of 3'-adenylated dinucleoside polyphosphates by specific enzymes degrading dinucleoside polyphosphates

51%

Guranowski A. , Sillero A. , Gunther-Sillero M. A.

|

nr 1

EN

Several 3' -[32 P]adenylated dinucleoside polyphosphates (NpnN' p*As) were synthesized by the use of poly(A) polymerase (Sillero MAG etal., 2001, Eur JBiochem.; 268: 3605-11) and three of them, ApppA[ 32P]A or ApppAp*A, AppppAp*A and GppppGp*A, were tested as potential substrates of different dinucleoside polyphosphate degrading enzymes. Human (asymmetrical) dinucleoside tetraphosphatase (EC 3.6.1.17) acted almost randomly on both AppppAp*A, yielding approximately equal amounts of pppA + pAp*A and pA + pppAp*A, and GppppGp*, yielding pppG + pGp*A and pG + pppGp*A. Narrow-leafed lupin (Lupinus angustifolius) tetraphosphatase acted preferentially on the dinucleotide unmodified end of both AppppAp*A (yielding 90% of pppA + pAp*A and 10 % of pA + pppAp*A) and GppppGp*A (yielding 89% pppG + pGp*A and 11% of pG + pppGp*A). (Symmetrical) dinucleoside tetraphosphatase (EC 3.6.1.41) from Escherichia coli hydrolyzed AppppAp*A and GppppGp*A producing equal amounts of ppA + ppAp*A| and ppG + ppGp*A, respectively, and, to a lesser extent, ApppAp*A producing pA + ppAp*A. Two dinucleoside triphosphatases (EC 3.6.1.29) (the human Fhit protein and the enzyme from yellow lupin (Lupinus luteus)) and dinucleoside tetraphosphate phosphorylase (EC 2.7.7.53) from Saccharomyces cerevisiae did not degrade the three 3 -adenylated dinucleoside polyphosphates tested.

5

Hint2, the mitochondrial nucleoside 5’-phosphoramidate hydrolase; properties of the homogeneous protein from sheep (Ovis aries) liver

38%

Bretes E. , Wojdyla-Mamon A. M. , Kowalska J. , Jamielity J. , Kaczmarek R. , Baraniak J. , Guranowski A.

|

nr 2

EN

Adenosine 5'-phosphoramidate (NH2-pA) is a rare natural nucleotide and its biochemistry and biological functions are poorly recognized. All organisms have proteins that may be involved in the catabolism of NH2-pA. They are members of the HIT protein family and catalyze hydrolytic splitting of NH2-pA to 5'-AMP and ammonia. At least five HIT proteins have been identified in mammals; however, the enzymatic and molecular properties of only Fhit and Hint1 have been comprehensively studied. Our study focuses on the Hint2 protein purified by a simple procedure to homogeneity from sheep liver mitochondrial fraction (OaHint2). Hint1 protein was also prepared from sheep liver (OaHint1) and the molecular and kinetic properties of the two proteins compared. Both function as homodimers and behave as nucleoside 5'-phosphoramidate hydrolases. The molecular mass of the OaHint2 monomer is 16 kDa and that of the OaHint1 monomer 14.9 kDa. Among potential substrates studied, NH2-pA appeared to be the best; the Km and kcat values estimated for this compound are 6.6 µM and 68.3 s-1, and 1.5 µM and 11.0 s-1 per natively functioning dimer of OaHint2 and OaHint1, respectively. Studies of the rates of hydrolysis of different NH2-pA derivatives show that Hint2 is more specific towards compounds with a P-N bond than Hint1. The thermostability of these two proteins is also compared.