708-79-2Relevant articles and documents
Effects of pH and temperature on the reaction of milk xanthine oxidase with 1-methylxanthine
Sau, Apurba Kurnar,Mondai, Madhu Sudan,Mitra, Samarcsh
, p. 3688 - 3692 (2000)
The reaction of milk Xanthine Oxidase (XO) with 1-methylxanthine has been investigated by steady state and stopped flow transient kinetic studies to understand the effect of a methyl group substituent on the purine ring. The pH dependence of the steady state kinetic parameter (Vmax/Km) shows a bell-shaped curve implying at least two ionisable groups are involved in the binding of XO with 1-methylxanthine, the higher pKa 7.7 corresponding to ionisation of the substrate and the lower one 6.2 to the enzyme (possibly Glu-1261 by analogy to Glu-869 of aldehyde oxidoreductase from Desulfovibrio gigas). The temperature dependence of the steady state and transient kinetic studies suggests the existence of at least one molecular intermediate during breakdown of the enzymesubstrate complex. The thermodynamic parameters of the microscopic rate constants were determined from the temperature dependence studies. The Royal Society of Chemistry 2000.
Synthesis of 3-Alkyl-6-Phenyl-4(3H)-pteridinones and their 8-Oxides. Potential Substrates of Xanthine Oxidase
Meester, J. W. G. De,Kraus, W.,Plas, H. C. van der,Brons, H. J.,Middelhoven, W. J.
, p. 1109 - 1116 (2007/10/02)
Synthetic routes for the preparation of 3-alkyl-6-phenyl-4(3H)-pteridinines 6 and their corresponding 8-oxides 5 (R=CH3, C2H5, (CH2)2CH3, (CH2)3CH3, CH(CH3)C2H5, CH(CH3)2 and CH(C2H5)CH2OCH(OC2H5)2) are described and their reactivities towards xanthine oxidase from Arthrobacter M-4 are determined.Only the 3-methyl derivative of 6-phenyl-4(3H)-pteridinone and its 8-oxide i.e. 6a and 5a are found to be substrates although their reactivities are still very low.Oxidation takes place at C-2 of the pteridinone nucleus.All the 3-alkyl derivatives are less tightly bound to t he enzyme than 6-phenyl-4(3H)-pteridinone.Introduction of the N-oxide at N-8 considerably lowers the binding of the substrates.Inhibition studies have revealed that 3-methyl-6-phenyl-4(3H)-pteridinone (6a) is non-competitive inhibitor with a Ki-value of 47 μM and the 3-ethyl derivative (6b) an uncompetitive one with a Ki-value of 19.6 μM.
