Degradation of phytate in the gut of pigs--pathway of gastro-intestinal inositol phosphate hydrolysis and enzymes involved

Abstract

The present study gives an overview on the whole mechanism of phytate degradation in the gut and the enzymes involved. Based on the similarity of the human and pigs gut, the study was carried out in pigs as model for humans. To differentiate between intrinsic feed phytases and endogenous phytases hydrolysing phytate in the gut, two diets, one high (control diet) and the other one very low in intrinsic feed phytases (phytase inactivated diet) were applied. In the chyme of stomach, small intestine and colon inositol phosphate isomers and activities of phytases and alkaline phosphatases were determined. In parallel total tract phytate degradation and apparent phosphorus digestibility were assessed. In the stomach chyme of pigs fed the control diet, comparable high phytase activity and strong phytate degradation were observed. The predominant phytate hydrolysis products were inositol phosphates, typically formed by plant phytases. For the phytase inactivated diet, comparable very low phytase activity and almost no phytate degradation in the stomach were determined. In the small intestine and colon, high activity of alkaline phosphatases and low activity of phytases were observed, irrespective of the diet fed. In the colon, stronger phytate degradation for the phytase inactivated diet than for the control diet was detected. Phytate degradation throughout the whole gut was nearly complete and very similar for both diets while the apparent availability of total phosphorus was significantly higher for the pigs fed the control diet than the phytase inactivated diet. The pathway of inositol phosphate hydrolysis in the gut has been elucidated.