Extended Data Fig. 6: Sea stars and sea cucumbers make unusual sterols.
From: Biosynthesis of saponin defensive compounds in sea cucumbers
a, Representative GC-MS profiles (TICs) of sea urchin, sea star and sea cucumber adult tissues. The peaks at 10.1, 10.4 and 11.52 min are lathosterol (7), episterol (22), and avenasterol (21), respectively. Peak eluting at 9.98 min unique to sea cucumbers and was characterized to be 14α-methylcholest-9(11)-en-3β-ol (11) (Supplementary Tables 5–7). b, Levels of cholesterol (5), lathosterol (7) and 14α-methylcholest-9(11)-en-3β-ol (11) in adult tissues of A. japonicus (mean ± SD, n = 2). Dw, dry weight (see Source Extended Data Fig. 6). c, Unusual sterols renders sea star and sea cucumber membranes saponin resistant. 3D conformations of cholesterol (5), lathosterol (7) and 14α-methylcholest-9(11)-en-3β-ol (11) showing flat conformation of side chain in 5 and bent conformation in 7 and 11. 3D conformations were optimized using Frog2 server with default parameters60. d, GC mass spectrum of the sterols observed. Avenasterol (21) and episterol (22) and were identified based on known spectra in the literature and others based on authentic standards. All sterols are TMS derivatives.
