“Lipase activity in hepatopancreas of the euryhaline crab Neohelice granulata: response in relation to osmoregulatory status”

MICHIELS, M.S.; PINONI,S.A.; DEL VALLE, J.C; LÓPEZ MAÑANES, A.A.

Encuentro; XXVII Annual Scientific Meeting Tucumán Biology Association; 2010

Studies on lipase activity in hepatopancreas (HP) of euryhaline crabs are lacking. We determined the occurrence, biochemical characteristics and response in relation to osmoregulatory status of lipase activity in the HP of N. granulata. Adult male crabs (n=4) were acclimated for 10 days in 35 ‰ salinity (S) (characterization) or in 35‰ (osmoconformation), 10‰ (hyperegulation) and 45‰ S (hyporegulation). The supernatant (10000xg 15min) from a HP homogenate (0.1 M Tris-HCl, pH 7.4; 4ml x g of tissue-1) was used. Lipase activity (μmol pNPx min-1x mgprot-1) was assayed by hydrolysis of pNPpalmitate (substrate curve:0.09-0.9 mM; Tris/HCl 50mM, pH 8.5, 37ºC) (pH curve: phosphate 5.4-6.4;Tris/HCl 7,2- 8,5; glycine 10.0; pNPP 0.7 mM, 37ºC) (temperature curve: 4-45°C, pNPP 0.7 mM, pH 8.5). Lipase activity was higher at pH 8.5 (activity at pHs 5.4-7.2= 50-70%, and at pH10.0= 27% of the activity at pH8.5); maximal at 37°C (activity at 4-20 and 45ºC= 40-50% lower); exhibited Michaelis-Menten kinetics (Km=0.18 mM; pH 8.5, 37ºC), and it was lower in 10 S (55±35) and 45 S(63±18) than in 35 ‰ S (120±39) (ANOVA p