In vitro and in vivo comparison of phytic acid dephosphorylation mechanisms by 3- and 6-phytases in broiler diets

Diets for farmed monogastric animals are supplemented with phytase to improve the bioavailability of phosphorus. Commercially, 6-phytases are preferred over 3-phytases due to differences in their sources, kinetics, and optimal operational pH. We examined both in vitro and in vivo dephosphorylation of phytate phosphorus by 3- and 6-phytases using high-resolution mass spectrometry to identify phytic acid, inositol phosphate intermediates, and free inositol. In vitro, 3-phytases exhibited conversion rates similar to those of 6-phytases, converting over 95 % of phytic IP6 into IP2 or IP1 within one hour. However, mechanistic differences between the two enzymes were observed in vivo. For example, broilers fed 6-phytase exhibited higher levels of inositol in the crop and gizzard than those fed 3-phytase (3.1 mg/g vs 2.4 mg/g). No significant differences were observed in the ileum of animals supplemented with either phytase (approximately 9 mg/g). Overall, 3-phytases can be an effective alternative to the more commonly used 6-phytases for releasing phytate phosphorus in broiler diets.