Phytic Acid‐Induced Inhibition of Digestive Protease and α‐Amylase in Three Indian Major Carps: An in vitro Study

Abstract

Antinutritional effects of phytic acid (myoinositol hexaphosphate, IP6) on growth and digestibility in fish have been reported. However, specific effect of IP6 on the digestive enzymes in fish has not been addressed. In this study, inhibitory effect of synthetic IP6 (Phytic acid sodium salt, 90% purity) on the activity of the digestive protease and α-amylase in rohu, Labeo rohita; catla, Catla catla; and mrigal, Cirrhinus mrigala has been investigated in vitro. Graded levels (12.5, 25, 50, 100, 150, and 200 μg/mL) of IP6 were added to the reaction mixtures containing enzyme extracts and substrate solution in triplicate to detect any change in enzyme activity. Results of the experiment revealed that IP6 significantly inhibit/lower activities of the digestive enzymes in a dose-dependent manner, as evident from the regression equations (F values significant at P < 0.001 level). Apparently, irrespective of the fish species studied IP6-induced inhibition of α-amylase activity was greater than protease activity. Among the three fish species studied, C. mrigala appeared to be more sensitive to IP6 for both α-amylase and protease activity. Enzyme activity was least affected in C. catla. Results of the study might raise concern while incorporating IP6 rich plant-derived feed ingredients in aqua feed preparation.

Applications of plant ingredients for tropical and subtropical freshwater finfish: possibilities and challenges

“…). However, the amount of PA in plant‐derived ingredients varies depending on the plant parts (Khan & Ghosh ). Due to the high density of negatively charged phosphate groups, PA is highly reactive and easily binds with di‐ and trivalent cations and even macromolecules like protein, starch or lipid forming phytate compounds (Sabu et al .…”

“…). Moreover, it has been opined that PA or its salt form (phytate) remains mostly undigested by fish due to lack of endogenous intestinal phytase (Khan & Ghosh ).…”

“…). Furthermore, the effect of PA on the digestive enzymes, protease and α‐amylase, in fish has also been addressed in vitro in three Indian major carps: rohu, catla and mrigal (Khan & Ghosh ).…”

Inositol phosphates: health implications, methods of analysis, and occurrence in plant foods

“…The form of InsP can influence this effect, as the magnesium-potassium salt of InsP 6 showed a higher inhibitory strength than free InsP 6 (Onyango et al, 2008). InsP 6 has also been shown to inhibit several digestive enzymes such as α-amylase, lipase, and various proteinases (e.g., pepsin, trypsin, chymotrypsin) in fish and poultry (Denstadli et al, 2006;Khan and Ghosh, 2013;Liu et al, 2010). These effects may be explained by the non-specific bindings of InsPs with cationic moieties of amino acids and proteins, followed by the precipitation of these complexes at low pH levels.…”

Comparative efficacy of phytase from fish gut bacteria and a commercially available phytase in improving the nutritive value of sesame oilseed meal in formulated diets for fingerlings of rohu, Labeo rohita (Actinopterygii: Cypriniformes: Cyprinidae)

“…The presence of phytate in feed is undesirable as it chelates nutritionally important divalent cations like potassium, magnesium, zinc, iron, calcium, and copper, and proteins and amino acids, thereby rendering them biologically unavailable to the animal (Sardar et al 2007, Afi nah et al 2010, Krogdahl et al 2010. Phytic acid in the form of phytate also inhibits digestive enzymes in fi sh (Khan and Ghosh 2013). Thus, the inclusion of plant proteins in fi sh diets may cause increased phosphorus discharge into the environment and a reduction in growth resulting from the decreased bioavailability of minerals (Cao et al 2007(Cao et al , 2008.…”