The cytochrome system is widespread in nature — occurring in micro- 

 organisms, higher plants, and animals — and has been studied a great 

 deal in fish. Comparison of the amounts of cytochrome c in red and 

 white muscle of several species of fish shows red muscle" to be a much 

 richer source (Matsuura and Hashimoto 1°5U and Huys 195U). Crystalline 

 cytochrome c from heart muscle of the bonito ( Katsuwonus vagans , Lesson) 

 and tunny (Thymus alalunga , Gmelin) has been prepared (Hagihara et al, 

 1957 and Matsuura and Hashimoto 1955). Several cytochromes (a, 3.3 , 

 b, and c) from the octopus ( Octopus vulgaris Lam.) have been identified 

 (Ghiretti-Magaldi et al. 1957). Paleus (I9!?b) compared the amino acid 

 composition of cytochrome c from salmon, beef, and chicken. He found it 

 to be similar for these three cytochromes except for the presence of 

 three histidine groups per mole in beef and chicken cytochrome £ and 

 only two per mole in that of salmon. Attempts to isolate cytochrome c 

 from oyster muscle (Humphrey 19U7) and sea-urchin ( Arbacia) eggs (Yoas 

 1950 and Krahl 1950) have not been successful, indicating that it is 

 present in extremely small amounts, if at all. In contrast to the eggs, 

 sea urchin sperm does contain considerable cytochrome c (Ball and Meyer- 

 hof 19U0). Teas (1950) presents spectral evidence for the presence of 

 cytochrome a and b in Arbacia eggs. Other marine invertebrates contain- 

 ing cytochromes are horseshoe crab, squid, and lobster (Ball and Meyer- 

 hof 19 UO). Baldwin (1938) was unable to detect any cytochrome in Helix 

 pomatia by spectroscopic means. 



Terminal oxidative processes occurring in the oyster have been 

 investigated extensively by Humphrey (19b6 and 19U7). A study of in- 

 hibitors showed that the respiration of whole homogenate is strongly 

 inhibited by cyanide, selenite, and arsenate. Azide, arsenite, pyro- 

 phosphate, and iodoacetate also inhibit. Inhibitions by cyanide and 

 azide suggested the presence of cytochrome oxidase, which was confirmed 

 by an assay using ascorbic acid as a reductant. A correlation may be 

 made between the very low concentration of cytochrome found in oyster 

 muscle and the lack of oxygen-transporting pigment in the blood with 

 the low metabolism of the organism. Umemura (1951 b and c) found red 

 muscle of fish to contain greater cytochrome oxidase activity than did 

 liver, kidney, and ordinary muscle. In the toadfish, the concentration 

 of cytochrome oxidase is highest in the heart, kidney, and liver. Al- 

 though this distribution is similar to that found in the rat, the absol- 

 ute activity of cytochrome oxidase in the toadfish is only one- third as 

 much (Lazarow and Cooperstein 1951). During development of Oryzias eggs, 

 cytochrome oxidase activity was found to increase over an 8-day period 

 (Hishida and Nakano 195U) • An enzyme similar to cytochrome oxidase of 

 other animal tissues is present in Arbacia eggs (Krahl 1950 and leas 

 1950). The presence of cytochrome oxidase has been demonstrated in parti- 

 cles isolated from octopus muscle (Ghiretti-Magaldi et al. 1957 )> in 

 oyster muscle (Humphrey 19h7)» and in horseshoe crab, lobster, and squid 

 (Ball and Meyerhof 19 UO). Foster (1956) found cytochromeoxidase to be 

 concentrated in mitochondria from lobster leg and claw nerves and from 

 squid giant fiber nerves. 



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