THE ABSORPTION SPECTRA OF COMPOUNDS RELATED TO THE STEROLS

C4-monomethylsterol β-glucoside and its synthase in Aurantiochytrium limacinum mh0186

Thraustochytrids, unicellular marine protists, synthesize polyunsaturated fatty acids (PUFAs) and PUFA-containing phospholipids; however, little is known about their glycolipids and their associated metabolism. Here, we report two glycolipids (GL-A, B) and their synthases in Aurantiochytrium limacinum mh0186. Two glycolipids were purified from A. limacinum mh0186, and they were determined by gas chromatography, mass spectrometry and two-dimensional nuclear magnetic resonance to be 3-O-β-D-glucopyranosyl-stigmasta-5,7,22-triene (GL-A) and 3-O-β-D-glucopyranosyl-4α-methyl-stigmasta-7,22-diene (GL-B), both of which are sterol β-glucosides (β-SGs); the structure of GL-B has not been reported thus far. Seven candidate genes responsible for the synthesis of these β-SGs were extracted from the draft genome database of A. limacinum using the yeast sterol β-glucosyltransferase (SGT; EC 2.4.1.173) sequence as a query. Expression analysis using Saccharomyces cerevisiae revealed that two gene products (AlSGT-1 and 2) catalyze the transfer of glucose from UDP-glucose to sterols, generating sterylglucosides (SGs). Compared to AlSGT-1, AlSGT-2 exhibited wide specificity for sterols and used C4-monomethylsterol to synthesize GL-B. The disruption of alsgt-2 but not alsgt-1 in strain mh0186 resulted in a decrease in total SG and almost complete loss of GL-B, indicating that AlSGT-2 is responsible for the synthesis of β-SGs in A. limacinum mh0186, especially GL-B, which possesses a unique sterol structure.

Response of plasma-25-hydroxyvitamin D to ultraviolet irradiation in long-stay geriatric patients

The response of plasma-25-hydroxyvitamin D (25[OH]D) to different exposures to ultraviolet irradiation has been studied in patients in long-stay geriatric wards. Increases sufficient to bring the plasma-25(OH)D into the normal range may be obtained with doses less than those required to produce erythema. The provision of such background irradiation may be a suitable method of preventing vitamin-D deficiency in elderly subjects who receive very little exposure to sunlight.