[The effect of anionic complexes on cytochrome c oxidation by cytochrome c oxidase].

The effect of different buffer anions on the maximal velocity (Vmax) and Michaelis constant (Km) of the first reaction between horse cytochrome c and beef cytochrome c oxidase was studied. The Michaelis constant for the high affinity phase varies little as the buffer anions borate, phosphate, succinate and citrate were employed, but Vmax varies significantly. At the ionic strength I = 0.

Surface potential changes of mitoplasts in the presence of pyridoxal phosphate modified cytochromes c.

1. The addition of native cytochrome c to mitoplasts leads to a decrease of surface potential of the mitoplast membrane. However the surface potential is slightly decreased (approximately 3 mV) when PLP(Lys 86)-cytochrome c and PLP(Lys 79)-cytochrome c were added.

Interaction of pyridoxal phosphate modified cytochromes c with mitoplasts.

1. The stability of the native conformation of the heme crevice of pyridoxal phosphate (PLP)-ferricytochromes c as assayed by the pK, for 695 nm absorption band varies considerably. The pKa values are 8.

Pyridoxal phosphate modified cytochromes c. Identification and electron transfer properties.

The preparation, purification and characterization of the three singly, three doubly and one triply substituted derivatives of cytochrome c modified by pyridoxal phosphate (PLP) at lysine residues are reported. The PLP positions in PLP derivatives were determined by the amino acid analysis and sequence of PLP peptides. The results identified the lysine at position 86 in one of the singly substituted, lysine 79 in the other singly substituted and lysines 86 and 79 in the third doubly substituted cytochrome c derivatives.

Charge interactions of cytochrome c with cytochrome c oxidase.

The pyridoxal phosphate (PLP) modification of the lysine amino groups in cytochrome c causes decrease in the reaction rate with cytochrome c oxidase. The rate constants for (PLP)2-cyt. c, PLP(Lys 86)-cyt.