Loss of tryptophan associated with photopolymerization and yellowing of proteins exposed to light over 300nm

Abstract

S-Carboxymethyl-lysozyme and S-carboxymethyl-ribonuclease A were irradiated with light of wavelength greater than 300nm. Photo-oxidative loss of tryptophan from the S-carboxymethyl-lysozyme was accompanied by yellowing of the protein and the formation of covalently cross-linked polymers. S-Carboxymethyl-ribonuclease, which contains no tryptophan, showed little yellowing and no polymer formation. The irradiated S-carboxymethyl-lysozyme was similar to the proteins of the brown cataractous human lens nucleus and to bovine lens proteins exposed to sunlight in vitro in that it (1) was insoluble in non-denaturing solvents, (2) contained a new fluorescence, (3) was brown in colour, and (4) contained covalent cross-links that are not disulphide bonds.

Photochemical Reactions Between Tryptophan and Polynucleotides*

“…During irradiation of 14C-trppolynucleotide solutions (or I4C-trp solutions alone) small amounts of I4C-trp polymers were produced. Such photopolymerization reactions of indole compounds has been reported earlier (Dilley, 1973). While these trp photopolymers also were precipitated with trichloroacetic acid, they were subsequently removed from the polyr~ucleotide-'~C-trp complex by the cold 95% ethanol wash.…”

Hydroxocobalamin association during cell culture results in pink therapeutic proteins

“…7,11 The occurrences spanned multiple products, processes, sites and manufacturing scales over several years, and the color varied in intensities. Pink coloration usually did not occur with every production run, making investigation of the root cause problematic.…”

Occurrence ofN-Formylkynurenine in Extracts ofNeurospora crassa: Evidence for the Activity of Tryptophan Pyrrolase

“…Perhaps the failure to detect the activity could mean that the enzyme per se does not occur in Neurospora and that the oxidative involve oxidative cleavage of the pyrrole ring to yield N-formylkynurenine (21); and (iii) photooxidation of lysozyme has been reported to involve the conversion of tryptophan residues to kynurenine (4). Alternatively, the failure to detect tryptophan pyrrolase in extracts of Neurospora could indicate the extreme lability of the enzyme.…”