Eritadenines - Novel type of potent inhibitors of S-adenosyl-L-homocysteine hydrolase

1982 ◽  
Vol 47 (1) ◽  
pp. 167-172 ◽  
Author(s):  
Ivan Votruba ◽  
Antonín Holý
Keyword(s):  
Catalytic Activity ◽  
Rat Liver ◽  
Hydrolytic Reaction

Rat liver SAH-hydrolase is strongly inhibited by four stereoisomeric 4-(adenin-9-yl)-2,3-dihydroxybutyric acids (eritadenines). D-Eritadenine, which is the most effective of the four, inactivates the catalytic activity of SAH-hydrolase at IC50 = 1.2 .10-8 mol l-1 in the hydrolytic reaction. The enzyme is irreversibly inhibited (τ/2 = 1.6 min). The inactivation activity decreases in the order D-erythro(2R, 3R) L-erythro(2S, 3S) threo(2S, 3R) threo(2R, 3S) configuration.

scholarly journals Nucleoside exchange catalysed by the cytoplasmic 5′-nucleotidase

1982 ◽  
Vol 205 (3) ◽  
pp. 503-510 ◽  
Author(s):  
Y Worku ◽  
A C Newby
Keyword(s):  
Rat Liver ◽  
Catalytic Mechanism ◽  
Physiological Role ◽  
Nucleoside Analogues ◽  
Rate Equations ◽  
Alternative Route ◽  
Purine Nucleotides ◽  
Pharmacological Agents ◽  
Hydrolytic Reaction ◽  
Hydrolysis Of

The inhibition of the cytoplasmic 5'-nucleotidase (EC 3.1.3.5) by its product, inosine, was studied with a partially purified preparation of the enzyme from rat liver. Inhibition of Pi production was found to be due to exchange of the inosine moiety between inosine and IMP. Exchange was not catalysed by reversal of the hydrolytic reaction, suggesting, instead, the mediation of an enzyme-phosphate intermediate. Two models for the catalytic mechanism are proposed and rate equations for the dependence of Pi production on inosine concentration are derived. The experimentally determined dependence was consistent with a mechanism in which hydrolysis of the enzyme-phosphate intermediate occurred only when it was unoccupied by inosine. This conclusion suggests that inosine analogues that cannot participate in exchange should inhibit the enzyme. Such inhibitors might be useful in defining the enzyme's physiological role or as pharmacological agents to decrease breakdown of purine nucleotides. The possibility that nucleoside exchange provides an alternative route for the phosphorylation of mutagenic or cytotoxic nucleoside analogues should also be considered.

scholarly journals Removal of an N-terminal peptide from mitochondrial aspartate aminotransferase abolishes its interactions with mitochondria in vitro

1985 ◽  
Vol 228 (3) ◽  
pp. 609-614 ◽  
Author(s):  
K M O'Donovan ◽  
S Doonan ◽  
E Marra ◽  
S Passarella ◽  
E Quagliariello
Keyword(s):  
Catalytic Activity ◽  
Rat Liver ◽  
Aspartate Aminotransferase ◽  
Terminal Segment ◽  
Model System ◽  
Native Enzyme ◽  
Cysteine Residues ◽  
Native Form ◽  
Mitochondrial Aspartate Aminotransferase

Treatment of mitochondrial aspartate aminotransferase from rat liver with trypsin leads to specific cleavage of the bonds between residues 26 and 27, and residues 31 and 32. The proteolysed enzyme has only a small residual catalytic activity, but retains a conformation similar to that of the native form as judged by accessibility and reactivity of cysteine residues. Proteolysis abolishes the ability of the enzyme either to bind to mitochondria or to be imported into the organelles. This suggests that the N-terminal segment of the native enzyme is essential for both of these functions, at least in the model system used to study the import process.

scholarly journals Molecular cloning and heterologous expression of a cDNA encoding a mouse glutathione S-transferase Yc subunit possessing high catalytic activity for aflatoxin B1-8,9-epoxide

1992 ◽  
Vol 285 (1) ◽  
pp. 173-180 ◽  
Author(s):  
J D Hayes ◽  
D J Judah ◽  
G E Neal ◽  
T Nguyen
Keyword(s):  
Catalytic Activity ◽  
Amino Acid ◽  
Amino Acid Sequence ◽  
Rat Liver ◽  
Cdna Clone ◽  
Aflatoxin B1 ◽  
Mouse Liver ◽  
High Catalytic Activity ◽  
Glutathione S Transferase ◽  
E Coli

Resistance to the carcinogenic effects of aflatoxin B1 (AFB1) in the mouse is due to the constitutive expression of an Alpha-class glutathione S-transferase (GST), YcYc, with high detoxification activity towards AFB1-8,9-epoxide. A cDNA clone (pmusGST Yc) for a murine GST Yc polypeptide has been isolated. Sequencing has shown the cDNA insert of pmusGST Yc to be 922 bp in length, with an open reading frame of 663 bp that encodes a polypeptide of M(r) 25358. The primary structure of the murine GST Yc subunit predicted by pmusGST Yc is in complete agreement with the partial amino acid sequence of the aflatoxin-metabolizing mouse liver GST described previously [McLellan, Kerr, Cronshaw & Hayes (1991) Biochem. J. 276, 461-469]. A plasmid, termed pKK-musGST Yc, which permits the expression of the murine Yc subunit in Escherichia coli, has been constructed. The murine GST expressed in E. coli was purified and found to be catalytically active towards several GST substrates, including AFB1-8,9-epoxide. This enzyme was also found to possess electrophoretic and immunochemical properties closely similar to those of the GST Yc subunit from mouse liver. However, the GST synthesized in E. coli and the constitutive mouse liver Alpha-class GST exhibited small differences in their chromatographic behaviour during reverse-phase h.p.l.c. Automated Edman degradation revealed alanine to be the N-terminal amino acid in the GST Yc subunit expressed in E. coli, whereas the enzyme in mouse liver possesses a blocked N-terminus. Although sequencing showed that the purified Yc subunit from E. coli lacked the initiator methionine, the amino acid sequence obtained over the first eleven N-terminal residues agreed with that predicted from the cDNA clone, pmusGST Yc. Comparison of the deduced amino acid sequence of the mouse Yc polypeptide with the primary structures of the rat Alpha-class GST enzymes revealed that it is more closely related to the ethoxyquin-induced rat liver Yc2 subunit than to the constitutively expressed rat liver Yc1 subunit. The significance of the fact that both mouse Yc and rat Yc2 exhibit high catalytic activity towards AFB1-8,9-epoxide, whereas rat Yc1 possesses little activity towards this compound, is discussed in terms of structure/function.

The HELLGH Motif of Rat Liver Dipeptidyl Peptidase III Is Involved in Zinc Coordination and the Catalytic Activity of the Enzyme

Biochemistry ◽  
1999 ◽  
Vol 38 (26) ◽  
pp. 8299-8303 ◽  
Author(s):  
Katsuhiko Fukasawa ◽  
Kayoko M. Fukasawa ◽  
Hiroyuki Iwamoto ◽  
Junzo Hirose ◽  
Minoru Harada
Keyword(s):  
Catalytic Activity ◽  
Rat Liver ◽  
Dipeptidyl Peptidase ◽  
Zinc Coordination

scholarly journals Stereoselectivity of rat liver glutathione transferase isoenzymes for α-bromoisovaleric acid and α-bromoisovalerylurea enantiomers

1988 ◽  
Vol 252 (1) ◽  
pp. 137-142 ◽  
Author(s):  
J M Te Koppele ◽  
B Coles ◽  
B Ketterer ◽  
G J Mulder
Keyword(s):  
Catalytic Activity ◽  
Rat Liver ◽  
Multigene Family ◽  
Glutathione Transferase ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Liver Glutathione ◽  
Amide Derivative ◽  
Isolated Rat

The stereoselectivity of purified rat GSH transferases towards alpha-bromoisovaleric acid (BI) and its amide derivative alpha-bromoisovalerylurea (BIU) was investigated. GSH transferase 2-2 was the only enzyme to catalyse the conjugation of BI and was selective for the (S)-enantiomer. The conjugation of (R)- and (S)-BIU was catalysed by the isoenzymes 2-2, 3-3 and 4-4. Transferase 1-1 was less active, and no catalytic activity was observed with transferase 7-7. Isoenzymes 1-1 and 2-2 of the Alpha multigene family preferentially catalysed the conjugation of the (S)-enantiomer of BIU (and BI), whereas isoenzymes 3-3 and 4-4 of the Mu multigene family preferred (R)-BIU. The opposite stereoselectivity of conjugation of BI and BIU previously observed in isolated rat hepatocytes and the summation of activities of enzymes known to be present in hepatocytes on the basis of present data are in accord.

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