Pyridoxal-5′-phosphate (P-5-P) is the bio-active form of vitamin B6, and is a catalyst for at least 113 known essential enzymatic reactions in the body including: homocysteine metabolism, for the production of serotonin and GABA. Studies show that people with compromised liver function and those with autism have an impaired ability to absorb conventional B6. Therefore, supplementing with P-5-P may be more indicated in these groups.