Other Coenzymes and Cofactors

Other Coenzymes and Cofactors.— The chemical synthesis of riboflavin phosphates and their acetyl derivatives has been reinvestigated. Riboflavin 4 -monophosphate (10) is an important contaminant of commercial flavin mononucleotide (FMN), and 

Pyridoxal 5 -phosphate (PLP) was noticed to be a constituent of rabbit muscle phosphorylase in 1957, and since that time it has been shown that all a-glucan phosphorylases which give phosphorolysis products with retention of configuration contain PLP. The exact role of the PLP is still not known, though it has been shown that these a-glucan phosphorylases have an absolute requirement for PLP and that the Schiflfbase formed between PLP and glycogen phosphorylase can be reduced with borohydride without eliminating the catalytic activity of the enzyme. The P n.m.r. spectrum of PLP bound to phosphorylase b shows that deprotonation of the 5 - 

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Mainly in archaebacteria the other coenzymes and cofactors occur in many organisms but not all synthesise them. 

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