Tryptophan—continued oxidation

The spectroscopic probe pyridine-N-oxide was used to characterize polar microdomains in reverse micelles in supercritical ethane from 50 to 300 bar. For both anionic and nonionic surfactants, the polarities of these microdomains were adjusted continuously over a wide range using modest pressure changes. The solubilization of water in the micelles increases significantly with the addition of the cosolvent octane or the co-surfactant octanol. Quantitative solubilities are reported for the first time for hydrophiles in reverse micelles in supercritical fluids. The amino acid tryptophan has been solubilized in ethane at the 0.1 wt.% level with the use of an anionic surfactant, sodium di-2-ethylhexyl sulfosuccinate (AOT). The existence of polar microdomains in aggregates in supercritical fluids at relatively low pressures, along with the adjustability of these domains with pressure, presents new possibilities for separation and reaction processes involving hydrophilic substances. 

Photo-oxidation of enzymes is often a very specific process, and continues to give useful evidence of their tertiary structure. Destruction of a single histidyl residue is observed for the photo-oxidation of the j82 subunit of tryptophan... 

The oxidation of tryptophan by various strains of Pseudomonas has been shown to proceed in all cases via kynurine. One sequence of reactions, the aromatic pathway, continues by eliminating the alanine side chain through the action of kynureninase, and subsequently utilizes oxygen for the formation of catechol and the pyrocatechase reaction already discussed. Another pathway retains the side chain of kynurenine and forms kynurenic acid through the action of kynurenine transaminase. A sequence of reactions has been indicated by recent work of Hayaishi and his associates (Kuno et al., 1961) this sequence appears to include three oxygenase reactions one hydroxylation and two phenolytic oxygenations (Fig. 18). 

---