[New aspects of vitamin and coenzyme research]

Vitamins are defined as essential organic micronutrients that are not synthesized by mammals. Coenzymes are defined as organic compounds with low molecular weight that are required to show enzyme activities by reversibly binding with their apoenzymes. Most of vitamins and coenzymes show various biofunctions besides their functions as vitamins and coenzymes. Accordingly, it is more appropriate to understand both as effective biofactors. Various retinoid derivatives synthesized bind to retinoid binding proteins to regulate gene expressions and show other biofunctions. Pyridoxal phosphate serves as an inhibitor of catepsins, and regulates the gene expression. Several novel built-in coenzymes such as topaquinone and lysyltyrosylquinone have been demonstrated in mammalian and microbial enzymes.