REACTIONS OF A GLUCOSINOLATE BREAKDOWN PRODUCT (BENZYL ISOTHIOCYANATE) WITH MYOGLOBIN

The interaction of various amounts of benzyl;Isothiocyanate (benzyl-IT C) with myoglobin is known to lead to the formation of derivatives. Th ese have been characterised by the determination of solubility, free a mino group, tryptophan content and chromatographic as well as electrop horetic behaviour. In the range between 2.5 and 125 mg benzyl-ITC/g pr otein, all properties of the reaction products correlate with the conc entration of benzyl-ITC. However, at 250 mg benzyl-ITC/g myoglobin, a rather unexpected low degree of derivatization, as well as atypical ch romatographic and electrophoretic behaviour, is observed. The proposed explanation was that conformational changes in the presence of a high concentration of hydrophobic benzyl-ITC made fewer amino groups acces sible to the reagent. To test this hypothesis we have run the reaction under denaturing conditions. The results showed that the reaction of myoglobin with high concentrations of benzyl-ITC in the presence of 8 M urea led to a higher degree of derivatization than in the presence o f water only. In addition, the Mr distribution of the reaction product s was determined by MALDI-TOF-mass spectrometry and the overall degree of derivatization calculated from the spectra. (C) 1998 Elsevier Scie nce Ltd. All rights reserved.