抄録
Crystalline aromatic L-aminoacid decarboxylase from Micrococcus percitreus is inactive in the absence of pyridoxal phosphate (PLP). The inactive form of the enzyme shows absorption at 340 nmand contains one mol of PLPper mol of enzyme. Binding of PLP to the inactive form is accompanied by a pronounced increase in absorbance at 415 nm. The amountof PLP that binds to this holoenzyme is 2 mol per mol of enzyme. The inactive half-resolved form, i. e. semiapoenzyme, is obtained again by dialysis of the holoenzyme against phosphate buffer.When the semiapoenzyme is dialyzed against phosphate buffer containing 3, 4-dihydroxyphenyl-L-alanine, it loses the absorption at 340 nm with the loss of PLP. This apoenzyme regains the activity and absorption at 340 nm and 415 nm on association with PLP.
