| Description |
The reactions of xanthydrol with various amino acids were investigated. Spectrophotometric measurements indicated that reactions occurred between xanthydrol and the amino acids arginine, asparagine, cysteine, glutamine, histidine, lysine and tryptophan. No reaction occurred with the amino acids alanine, ?-alanine, glycine, leucine, praline, hydroxy proline, threonine or the dipeptide glycyl-L-leucine. S-Xanthyl-cysteine was isolated as the hydrochloride. The xanthyl derivatives of N-carbobenzoxy-L-asparagine and N-carbobenzoxy-L-tryptophan were prepared in crystalline form. Hydrogenation of these compounds to remove the carbobenzoxy group was unsuccessful. N-Xanthyl nicotinamide was also prepared. The reaction products of xanthydrol and the amino acids were found to be quite unstable in solution pH 8.0 when placed in a water bath at 25? for 120 minutes or heated to 95? for 60 minutes at pH 2.5 with the exception of the tryptophan product. The violet-colored material isolated from a reaction between xanthydrol and tryptophan was stable in a mixture of 12N HC1 and glacial acetic acid or 6N NaOH when refluxed for 24 hours. Cytochrome c isolated by the producer developed by Keilin and Hartree (21) found to be electrophoretically homogeneous at pH 7.3 and pH 10.68 but inhomogeneous at pH 8.5. Chromatography on IRC-50 was effective in increasing the iron content of cytochrome c from 0.13% to 0.47%, It, too, was electrophoretically homogenous at pH 7.3 and pH 10.68 but was inhomogeneous at pH 8.5. Xanthydrol was found to react with cytochrome c. The xanthyl-cytochrome c was inactive when assayed in the succinoxidase system. A 2.66 molar excess of xanthydrol was found to cause a 63% inactivation whereas a 2 molar excess if xanthydrol caused none. Xanthydrol had no apparent effect on cytochrome c when assayed chemically. Xanthyl-cytochrome c was prepared by the reaction between xanthydrol and cytochrome c in 66% acetic acid. An average of 1.8 xanthyl residues were found per mol of cytochrome c. The xanthyl-cytochrome c had a mobility of +3.8cm.2/V/sec. x 10-5 at pH 7.3 compared with a mobility of +4.8 cm. 2/V/sec. x 10-5 of cytochrome c at the same pH. Numerous differences were noted between the absorption spectra of cytochrome c and xanthyl-cytochrome c. Xanthyl-cytochrome c was found to be an inhibitor of cytochrome c in the succinoxidase system. The chemically reduced xanthyl-cytochrome c could be oxidized enzymatically and did not inhibit the enzymatic oxidation of reduced cytochrome c. Oxidized xanthyl-cytochrome c could not be found in reduced enzymatically and inhibited the enxymatic reduction of oxidized cytochrome c. A three-fold excess of xanthyl-cytochrome c caused a 35% inhibition of cytochrome c in the succinoxidase system. Oxidized xanthyl-cytochrome c was not reduced by a soluble DPNH-cytochrome c reductase prepared from beef heart. |
