|Lei, Xingen - CORNELL UNIVERSITY|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2000
Publication Date: N/A
Interpretive Summary: Phytase is an enzyme that when used as an additive in animal feed can significantly reduce the amount of phosphorus in animal manure. This is important because many farm animals are fed soybean and other plant meals that are high in phytic acid, the major phosphorus storage site in many plants. Since pigs, chickens, and many other animals lack the phytase enzyme to break this compound down, their manure can have unacceptably high levels of phosphorus that can seriously impact our water ways. This study examined various phytases and found some with improved heat tolerance. Heat tolerance is a desirable feature because it allows more of the enzyme to survive the heating that is often necessary in processing soybean meal into animal feed. The primary beneficiaries of this research will be the animal feed industry, soybean growers and scientists.
Technical Abstract: Extracellular phytase from four Aspergillus fumigatus isolates were characterized and their genes cloned and sequenced. A correlation between lower optimum pH (4.0) and a higher optimum temperature (70 C) was found in these enzymes. Based on the banding pattern of the phytases in SDS-PAGE a similar level of glycosylation was present in all the enzymes. All four displayed a lower specific activity for phytic acid and were less resistant to proteolytic degradation than Aspergillus niger phytase. Very little sequence variation was found in any of the genes and no correlation is apparent between the sequence changes and the differences in the enzyme's characteristics. This suggests that differences in pH and temperature optimum in these four isolates of Aspergillus fumigatus may be due in part to subtle differences in post-translational modification.