Cytochrome components of mitochrondria in the maize weevil, Sitophilus zeamais(MOTSCH), were determined by the method of the reduced minus-oxidized difference spectra. The α-bands of the cytochrome components were observed mostly in the usual positions : Cyt. a, 603 nm; Cyt. b, 564 nm; Cyt. c, 551 nm, and the γ-peak of Cyt. a was also identified at 443 nm. Contents of these cytochromes were strongly similar to those in thoractic muscle mitochondria of the colorado porato beetle. The order of enzyme arrangement of the electron transport chain in the maize weevil mitochondria will most likely be similar to those of commonly observed mitochondria such as those of rat liver, beef heart, etc.The effect of phosphine (PH
3) on the difference spectrum of the maize weevil mitochondria was essentially similar to that observed with HCN treatment, and PH
3 strongly inhibited the respiration of the maize weevil mitochondria using substrates of pyruvate+malate, succinate, and ascorbate+TMPD.The obervations of the spectral change and the respiratory inhibition of maize weevil mitochondria by PH
3 suggest that PH
3 inhibits cytochrome oxidase.
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