In shallow marine teleost fishes, the osmolyte trimethylamine oxide (TMAO) is typically found at <70 mmol/kg wet weight. Recently we found deep-sea teleosts have up to 288 mmol/kg, increasing in the order shallow < bathyal < abyssal. We hypothesized that this protein stabilizer counteracts inhibition of proteins by hydrostatic pressure, and showed that, for lactate dehydrogenases (LDH), 250 mM TMAO fully offset an increase in NADH K(m) at physiological pressure, and partly reversed pressure-enhanced losses of activity at supranormal pressures. In this study, we examined other effects of pressure and TMAO on proteins of teleosts that live from 2000-5000 m (200-500 atmospheres [atm]). First, for LDH from a grenadier (Coryphaenoides leptolepis) at 500 atm for 8 hr, there was a significant 15% loss in activity (P < 0.05 relative to 1 atm control) that was reduced with 250 mM TMAO to an insignificant loss. Second, for pyruvate kinase from a morid cod (Antimora microlepis) at 200 atm, there was 73% increase in ADP K(m) without TMAO (P < 0.01 relative to K(m) at 1 atm) but only a 29% increase with 300 mM TMAO. Third, for G-actin from a grenadier (C. armatus) at 500 atm for 16 hr, there was a significant reduction of F-actin polymerization (P < 0.01 compared to polymerization at 1 atm) that was fully counteracted by 250 mM TMAO, but was unchanged in 250 mM glycine. These findings support the hypothesis. J. Exp. Zool. 289:172-176, 2001.
Copyright 2001 Wiley-Liss, Inc.