Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.3.5 (5'-nucleotidase)
 3,167 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thirty-three different flavonoids were screened for their ability to influence ATP-dependent Ca2+ uptake by rat liver plasma membrane vesicles. Nine of the flavonoids, at a concentration of 100 microM inhibited Ca2+ uptake by more than 20%. The remaining 24 flavonoids exhibited little or no effect. The relative order of potency of the more biologically active flavonoids was myricetin greater than butein greater than phloretin = luteolin greater than eriodictyol = silybin. Myricitrin and phloridzin, the glycosides of myricetin and phloretin, respectively, had no effect. The degree of inhibition caused by myricetin was concentration dependent and was also affected by the preincubation time. After 10 min of preincubation, 52 microM myricetin lowered the initial rate of 45Ca uptake by 50%. The inhibition by myricetin was non-competitive with respect to Mg-ATP and of a mixed type with respect to Ca2+. At a concentration of 100 microM, myricetin had no effect on several plasma membrane enzymes such as 5'-nucleotidase, alkaline phosphatase and a Ca2(+)-activated ATPase but inhibited K(+)-dependent p-nitrophenyl phosphatase by 83%. The ATP-dependent Ca2+ transport systems located on the plasma membrane or endoplasmic reticulum derived from other tissues were also inhibited by myricetin. Analysis of the structure-activity relationship revealed that lipid solubility and polyhydroxylation particularly at positions 5,7,3' and 4' of the flavonoid ring structure enhanced the ability of the flavonoid to inhibit Ca2+ uptake. The results suggest that inhibition of Ca2+ transport activity probably involves the interaction of the phenolic groups of the flavonoid with the Ca2+ transporting protein.
 ...
PMID:Effect of myricetin and other flavonoids on the liver plasma membrane Ca2+ pump. Kinetics and structure-function relationships. 199 24

A series of structurally related flavonoids and related compounds were evaluated whether they have inhibitory properties on the 5'-nucleotidase (5'-ribonucleotide phosphohydrolase; EC 3.1.3.5, 5'-NT) activity. Some of the flavonoids tested inhibit the enzyme such as quercetin, morin, apigenin, chrysin, myricetin, luteolin, diosmetin, (+/-)naringenin and diosmin. Rutin, naringin, hyperosid, (+/-)catechin, caffeic acid and rosmarinic acid had no inhibitory effect on the 5'-NT activity. Myricetin and quercetin were the most potent inhibitors for 5'-NT with IC50 values of 1.1 and 1.4 microM, respectively. Kinetic analysis showed a mixed type of inhibitor for both myricetin (Ki = 1.5 microM at pH 7.45), and quercetin (Ki = 0.6 microM at pH 7.45). The K(m) value for 5'-adenosine monophosphate (5-AMP) was determined with 77 microM at pH 7.45. The differential inhibitory potencies of flavonoids seem to be structurally related (hydroxylation pattern). The results demonstrate that some flavonoids are strong inhibitors of 5'-NT activity which can be correlated to their pharmacological effects.
 ...
PMID:In vitro effects of selected flavonoids on the 5'-nucleotidase activity. 1039 92