ABSTRACT
Different cytochromes are usually named after the type of heme they contain, such as a, b, and c. To further distinguish different proteins with the same type of heme, a subscript next to the heme type is used [17,18]. In certain cytochromes, such as cytochrome c2, c5 or c6, the subscript indicates the historical order of discovery. In other cytochromes, such as cytochrome C551 or C554, the subscript denotes the max imum electronic absorption peak of the a band in their reduced forms. Independent of the heme type, several axial ligations are possible for the heme iron in cytochromes, as reported in Table 1. A common feature of all electron transfer cytochromes, except cytochrome c\ is that their iron ion is hexa-coordinate. Their reduction potential values span from about +390 to —380 mV.
