Reconstitution of the pyridoxal 5′-phosphate (PLP) dependent enzyme serine palmitoyltransferase (SPT) with pyridoxal reveals a crucial role for the phosphate during catalysis

The pyridoxal 5'-phosphate (PLP)-dependent enzyme serine palmitoyltransferase (SPT) is required for de novo sphingolipid biosynthesis. A previous study revealed a novel and unexpected interaction between the hydroxyl group of the l-serine substrate and the 5'-phosphate group of PLP. By using pyridoxal (PL), the dephosphorylated analogue of vitamin B6, we show here that this interaction is important for substrate specificity and optimal catalytic efficiency.