Latest published research in phytate- protein interactions highlights differences between phytase enzymes in practice

While at first glance the relevance of the title to animal nutritionists may not be immediately obvious, this collaborative research by scientists from Lund University (Sweden) and Genencor studied interactions of phytate with dietary proteins as measured by the formation of insoluble complexes and the suitability of using the phytate-protein complex as a substrate for phytase assays. The authors demonstrated that, as phytate-protein complexes occurred in feed and the digestive tract of animals, this may be a more relevant substrate for the evaluation of phytases than sodium phytate, a laboratory chemical routinely used in traditional phytase assays. Of commercial interest was that the study included an independent evaluation of four different commercial phytases in their effectiveness to hydrolyze either synthetic sodium phytate, or naturally occurring protein-phytate complexes in feed at a pH of 3.0. Results shown in Table 1 firstly confirm that when sodium phytate (IP6-Na) is used as a substrate at low pH, the degree of Na-phytate hydrolysis is similar between the two E. coli phytases, but is significantly lower when fungal phytases (P. lycii and A. niger) are applied. These differences between E. coli and fungal phytase sources are not new and have been shown to be a function of the lower pH optimum of the E. coli phytases versus their fungal phytase counterparts (Wyss et al., 1999). However, of greater relevance to nutritionists are the large differences shown between commercial phytases in their ability to degrade protein-phytate complexes, being not only significantly different between E. coli and fungal phytases, but also between different E. coli phytase sources. As the main anti-nutritional effect of phytate is caused by the formation of insoluble protein-phytate complexes in the acid stomach this data provides the first strong evidence that the nutritional benefit from phytase enzymes can no longer be viewed as being constant within classes of phytase such as E. coli. Consequently, in practice, different matrix values should be applied in feed formulation to account for these differences.