Whitman W B, Tabita F R
Biochemistry. 1978 Apr 4;17(7):1282-7. doi: 10.1021/bi00600a023.
Ribulose 1,5-bisphosphate carboxylase isolated from Rhodospirillum rubrum was strongly inhibited by low concentrations of pyridoxal 5'-phosphate. Activity was protected by the substrate ribulose bisphosphate and to a lesser extent by other phosphorylated compounds. Pyridoxal phosphate inhibition was enhanced in the presence of magnesium and bicarbonate, but not in the presence of either compound alone. Concomitant with inhibition of enzyme activity, pyridoxal phosphate forms a Schiff base with the enzyme which is reversible upon dialysis and reducible with sodium borohydride. Subsequent to reduction of the Schiff base with tritiated sodium borohydride, tritiated N6-pyridoxyllysine could be identified in the acid hydrolysate of the enzyme. Only small amounts of this compound were present when the reduction was performed in the presence of carboxyribitol bisphosphate, an analogue of the intermediate formed during the carboxylation reaction. Therefore, it is concluded that pyridoxal phosphate modifies a lysyl residue close to or at the active site of ribulose bisphosphate carboxylase.
从深红红螺菌中分离出的1,5-二磷酸核酮糖羧化酶受到低浓度的5'-磷酸吡哆醛的强烈抑制。底物二磷酸核酮糖可保护该酶的活性，其他磷酸化化合物在较小程度上也有保护作用。在镁离子和碳酸氢根存在时，磷酸吡哆醛的抑制作用增强，但单独存在这两种化合物时则不会。伴随着酶活性的抑制，磷酸吡哆醛与该酶形成席夫碱，经透析后该席夫碱可逆，且能用硼氢化钠还原。用氚化硼氢化钠还原席夫碱后，在该酶的酸水解产物中可鉴定出氚化的N6-吡啶基赖氨酸。当在羧基核糖醇二磷酸（羧化反应过程中形成的中间体类似物）存在下进行还原时，仅存在少量这种化合物。因此，可以得出结论，磷酸吡哆醛修饰了靠近或位于二磷酸核酮糖羧化酶活性位点的赖氨酸残基。
