“Sucrase activity in the hepatopancreas of the euryhaline crab Cyrtograpsus angulatus: response to environmental salinity”,

ASARO, A.; DEL VALLE, J.C; LÓPEZ MAÑANES, A.A.

Encuentro; XXVII Annual Scientific Meeting Tucumán Biology Association; 2010

The underlying digestive adjustments (i.e. activity of key digestive enzymes) in relation to osmoregulatory status in euryhaline crabs are unknown. Moreover, knowledge of digestive biochemical characteristics of euryhaline crabs is still scarce and fragmentary. The aim of this work was to determine the occurrence, biochemical characteristics and response to low salinity of sucrase (suc) activity in the hepatopancreas (HP) of C. angulatus. Adult males crabs were acclimated 10 days in 35‰ salinity (S) (characterization) or 35‰ (osmoconformation) and 10‰S (hyperregulation). The supernatant (10000xg 15min) from a HP homogenate (0.1M Tris- HCl, pH 7.4) (4ml buffer x g of tissue-1) was used. Suc activity (μgglucose x min-1 x mgprotein-1) was assayed by hydrolysis of sucrose in 0.1 M maleate/OHNa 30ºC (pH curve: 3.5-8.3, sucrose=28mM; substrate curve: sucrose=2.8-42mM, pH=5.2; salinity: sucrose=42mM, pH=5.2). Suc activity were high over a wide range of pH, exhibited Michaelis-Menten kinetics (Km(mM)=14.26±5.81) and was lower (about 86%) in 10‰S than in 35‰ S (183.85 ± 40.31) (Kruskal-Wallis; H= 6.8; p = 0.008). The results showed the existence of a high sucrase activity sensitive to salinity in the hepatopancreas of C. angulatus, suggesting a role in adjustments at the biochemical level underlying osmorregulation.