In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Use of 8-Substituted-FAD Analogues To Investigate the Hydroxylation Mechanism of the Flavoprotein 2-Methyl-3-hydroxypyridine-5-carboxylic Acid Oxygenase, published in 2004-04-06, which mentions a compound: 27828-71-3, Name is 5-Hydroxynicotinic acid, Molecular C6H5NO3, Name: 5-Hydroxynicotinic acid.
2-Methyl-3-hydroxypyridine-5-carboxylic acid (MHPC) oxygenase (MHPCO) is a flavoprotein that catalyzes the oxygenation of MHPC to form α-(N-acetylaminomethylene)-succinic acid. Although formally similar to the oxygenation reactions catalyzed by phenol hydroxylases, MHPCO catalyzes the oxygenation of a pyridyl derivative rather than a simple phenol. Therefore, in this study, the mechanism of the reaction was investigated by replacing the natural cofactor FAD with FAD analogs having various substituents (-Cl, -CN, -NH2, -OCH3) at the C8-position of the isoalloxazine. Thermodn. and catalytic properties of the reconstituted enzyme were investigated and found to be similar to those of the native enzyme, validating that these FAD analogs are reasonable to be used as mechanistic probes. Dissociation constants for the binding of MHPC or the substrate analog 5-hydroxynicotinate (5HN) to the reconstituted enzymes indicate that the reconstituted enzymes bind well with ligands. Redox potential values of the reconstituted enzymes were measured and found to be more pos. than the values of free FAD analogs, which correlated well with the electronic effects of the 8-substituents. Studies of the reductive half-reaction of MHPCO have shown that the rates of flavin reduction by NADH could be described as a parabolic relationship with the redox potential values of the reconstituted enzymes, which is consistent with the Marcus electron transfer theory. Studies of the oxidative half-reaction of MHPCO revealed that the rate of hydroxylation depended upon the different analogs employed. The rate constants for the hydroxylation step correlated with the calculated pKa values of the 8-substituted C(4a)-hydroxyflavin intermediates, which are the leaving groups in the oxygen transfer step. It was observed that the rates of hydroxylation were greater when the pKa values of C(4a)-hydroxyflavins were lower. Although these results are not as dramatic as those from analogous studies with p-hydroxybenzoate hydroxylase, they are consistent with the model that the oxygenation reaction of MHPCO occurs via an electrophilic aromatic substitution mechanism analogous to the mechanisms for p-hydroxybenzoate and phenol hydroxylases.
This compound(5-Hydroxynicotinic acid)Name: 5-Hydroxynicotinic acid was discussed at the molecular level, the effects of temperature and reaction time on the properties of the compound were discussed, and the optimum reaction conditions were selected.
Reference:
Chapter 1 An introduction to palladium catalysis,
Palladium/carbon catalyst regeneration and mechanical application method