Interaction between pyridoxal kinase and pyridoxine-5-P oxidase, two enzymes involved in the metabolism of vitamin B6.

Pyridoxine-5-P oxidase has been purified 2000-fold from pig brain.The enzyme preparation migrates as a single protein and activity band on analytical gel electrophoresis.The enzyme binds the cofactor FMN with a dissociation constant lower than lo-* M and it is made up of two subunits of 30,000 molecular weight.Pyridoxine-5-P oxidase catalyzes the oxidation of pyridoxine-5-P (KM = 1.3 X lo-' M) and it is inhibited by pyridoxal-5-P (K, = 2.3 x lo-' M). Interaction between Enzymes 887also gives results which are consistent with a model which assumes direct physical interaction between the two enzymes.This method has been previously used to deduce proximity relationship between the catalytic sites of aspartate aminotransferase (21) and to study the distance of separation between the subunits of oligomeric protein structures (22-24).