Cutaneous Metabolism of Vitamin B-6

The study "Cutaneous Metabolism of Vitamin B-6" investigated the metabolism of vitamin B-6 in human and mouse skin, hamster melanomas, and various cell lines. It found that pyridoxamine 5'-phosphate content was higher in mouse and hamster skin compared to human skin, and rapidly growing melanomas exhibited increased activity of pyridoxamine 5'-phosphate oxidase and pyridoxal 5'-phosphate hydrolase. The study suggested that an enzyme other than tissue-nonspecific alkaline phosphatase (TNAP) might be responsible for cutaneous pyridoxal 5'-phosphate hydrolase activity, as TNAP knockout mice maintained normal skin histology and TNAP mRNA was not detected in HaCaT cells or human skin. Additionally, enzyme activities such as PMP oxidase and PLP hydrolase increased during certain phases of the hair cycle in mouse skin and in rapidly growing melanomas. The findings indicated that skin PLP hydrolase activity might be associated with an enzyme other than TNAP.