C-13 AND P-31 NMR ANALYSES OF THE CULTURED POSTERIOR SILK GLAND OF THE SILKWORM, BOMBYX-MORI - SILK FIBROIN PRODUCTION AND THE EFFECT OF SORBITOL-6-PHOSPHATE

The posterior silk gland from 5th-instar Bombyx mori larvae which produces silk fibroin, was cultured in vitro, and the tissue was monitored by 13C and 31P NMR spectroscopy to determine the degree of silk fibroin production and the physiological state of the tissue. The protein produced in the cultured tissue was confirmed electrophoretically to be silk fibroin. [1-13C]glycine added to the culture medium was incorporated into the silk fibroin in the tissue. The 31P NMR spectrum of the tissue showed several peaks of sugar phosphates, such as glucose-6-phosphate, fructose-6-phosphate and fructose-1,6-bisphosphate, together with those of phosphoenolpyruvate, uridine 5′-diphosphoglucose and inorganic phosphate. The intensities of these peaks decreased with time during culture indicating gradual loss of activity of the tissue. Addition of sorbitol-6-phosphate, which is present at high concentration in the larval hemolymph of B. mori, to the culture medium, reduced the rate of decrease of the peak intensities, indicating that this polyol phosphate was effective for maintaining the physiological activity of the silk gland in vitro. © 1990.