The inorganic chemistry of the cobalt corrinoids - an update

The inorganic chemistry of the cobalt corrinoids, derivatives of vitamin B₁₂, is reviewed, with particular emphasis on equilibrium constants for, and kinetics of, their axial ligand substitution reactions. The role the corrin ligand plays in controlling and modifying the properties of the metal ion is emphasised. Other aspects of the chemistry of these compounds, including their structure, corrinoid complexes with metals other than cobalt, the redox chemistry of the cobalt corrinoids and their chemical redox reactions, and their photochemistry are discussed. Their role as catalysts in non-biological reactions and aspects of their organometallic chemistry are briefly mentioned. Particular mention is made of the role that computational methods - and especially DFT calculations - have played in developing our understanding of the inorganic chemistry of these compounds. A brief overview of the biological chemistry of the B₁₂-dependent enzymes is also given for the reader's convenience.

Versatile Enzymology and Heterogeneous Phenotypes in Cobalamin Complementation Type C Disease

Nutritional deficiency and genetic errors that impair the transport, absorption, and utilization of vitamin B₁₂ (B₁₂) lead to hematological and neurological manifestations. The cblC disease (cobalamin complementation type C) is an autosomal recessive disorder caused by mutations and epi-mutations in the MMACHC gene and the most common inborn error of B₁₂ metabolism. Pathogenic mutations in MMACHC disrupt enzymatic processing of B₁₂, an indispensable step before micronutrient utilization by the two B₁₂-dependent enzymes methionine synthase (MS) and methylmalonyl-CoA mutase (MUT). As a result, patients with cblC disease exhibit plasma elevation of homocysteine (Hcy, substrate of MS) and methylmalonic acid (MMA, degradation product of methylmalonyl-CoA, substrate of MUT). The cblC disorder manifests early in childhood or in late adulthood with heterogeneous multi-organ involvement. This review covers current knowledge on the cblC disease, structure–function relationships of the MMACHC protein, the genotypic and phenotypic spectra in humans, experimental disease models, and promising therapies.

Bioinformatic and chemoneurocytological analysis of the pharmacological properties of vitamin B12 and some of its derivatives

More than three thousand five hundred biological properties of vitamin B[Formula: see text] and four of its derivatives (aquacobalamin, cyanoaquacobyrinic acid heptamethyl ester, dicyanocobyrinic acid heptamethyl ester and stable yellow corrinoid) have been assessed by bioinformation analysis. Based on the data obtained (including the assessments of the interaction of molecules with the proteins of rat proteome), conclusions were drawn about the potential effects and safety of the investigated substances. In particular, it has been shown that heptamethyl esters of cyanoaquacobyrinic and dicyanocobyrinic acids, as well as a stable yellow corrinoid (antivitamin), can be recommended for further study as analgesics, anti-inflammatory drugs and, also, antitumor agents aimed at the therapy of glioblastoma, hepatoblastoma and T-cell leukemia. Estimates of the LD50 constants for rats and the TD50 and IC50 constants for rat muscle cells in culture, along with the results of assessments of the interaction of molecules with the rat proteome, showed that all the compounds studied were of low toxicity. At the same time, cyanocobalamin and aquacobalamin are distinguished by the least cumulative properties in comparison with other studied compounds. Chemoneurocytological analysis of compounds showed that cyanocobalamin and aquacobalamin may have the greatest neuroprotective effects: increase in the concentration of the substances by 1 mmol/l causes the estimate of neuronal survival to increase by 25%.

The radical versus ionic mechanisms of reduced cobalamin inactivation by tert-butyl hydroperoxide and hydrogen peroxide in aqueous solution

It was demonstrated that antioxidants cannot protect reduced cobalamin against its modification by hydrogen peroxide.

Kinetics and mechanism of the reaction of cyanocobalamin with potassium hydroxide in non-aqueous media

The reaction of cyanocobalamin (CNCbl) with potassium hydroxide (KOH) was studied in isopropyl alcohol (iPrOH) and dimethyl sulfoxide (DMSO) under anaerobic conditions.