N-aminopeptidase activity in hepatopancreas of euryhaline crab Neohelice granulata

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

Encuentro; XV Annual Meeting Argentine Biology Society; 2013

Little is known about N-Aminopeptidase activity (APN) in hepatopancreas (H) of euryhaline crabs. We studied the occurrence, biochemical characteristics and responses to salinity of APN in H of N. granulata. Adult males (n=5) were acclimated 10 days in 35, 10 and 45? salinity (S) (osmoconformation, hyper and hypo-regulation, respectively). The supernatant (10000xg 15 min) (homogenate:Tris-HCl 0.1M, pH 7.4 ; 4mlxg of tissue-1) was used. APN (μmolesxmin-1xmgprot-1) was colorimetrically quantified (curve substrate: 0.083-0.500 mM in Tris/HCl 50mM, pH 7.6, 37ºC); (pH curve: buffers pH 6.6-9: Tris/HCl; 10.0: Glycine; L-alanine 0.42 mM, 37ºC); temperature curve: 4-50 °C; L-alanine 0.42 mM, pH 7.6). APN was higher at pH 7.6 and 8.5-9.0 and (% of maximal activity): 25,41,40 at pH 6.6, 8.0 and 10.0. APN was higher at 37 °C and (% of maximal activity): 45(4 ºC), 35 (20º and 30 ºC), 98 (45 ºC), 75 (50ºC). APN showed Michaelis-Menten kinetics (Km= 0.11 mM) (pH 7.6, 37 ºC). APN was higher in 10? (3184±328) and 37?S (5720±1242) than in 35?S (2202±268).The results suggest the role of APN in digestive adjustments upon hyper and hyporegulation