Biological role of formaldehyde, and cycles related to methylation, demethylation, and formaldehyde production.

An overview is given on the analysis, formation, role and occurrence of formaldehyde in living organisms. Various methods have been used for the determination of formaldehyde in tissues and body fluids. Gas chromatography, thin-layer chromatography and HPLC were employed for the analysis of formaldehyde, mainly after derivatization. The formaldehyde level of human blood and urine was found at the low ppm level. The formaldehyde level could be increased upto several ten micro g/mL(-1) following special dietary supply. Biochemical pathway of both the formaldehyde production and demethylation/methylation processes is generally connected to the methionine - homocysteine cycles. Another important way of demethylation generated formaldehyde production is given by microsomal cytochrome P-450 dependent oxidation of xenobiotics, such as various drugs prescribed by doctors. Semicarbazide sensitive amine oxidase also produces formaldehyde. Increased level of formaldehyde may be the indication of either patho-physiological processes, or environmental contamination, or malnutrition. The formaldehyde-related methylation and demethylation procedures are also detailed. DNA methylation may have an important role in the pathogenesis of certain diseases.