1a.Objectives (from AD-416)
First, develop phytases with significantly higher specific activity and broad substrate utilization by employing molecular biology techniques. Second, engineer higher heat stability in phytase and combine this with increased specific activity to produce a more cost effective enzyme for the animal feed industry. This will be followed by optimizing the enzymatic and nutritional properties of phytase for specific applications.
1b.Approach (from AD-416)
Analyze the sequence and molecular structural data on phytase molecules to achieve higher specific activity for phytic acid and then mutate the substrate specificity site and neighboring amino acid residues in A. niger NRRL 3135 phyA to effect these changes. These same techniques will also be employed to widen the variety of substrates that can be utilized. Increase heat tolerance in phytase will be effected by replacement of specific amino acid residues in the phyA molecule with amino acids occurring at higher frequency in stable proteins; this will result in a mutant phyA with increased heat tolerance. Once this goal is achieved, a combination of increased thermostability with the mutations conferring the higher specific activity will be undertaken. Determination of whether phytate binds to and affects the solubility of chromium and molybdenum, and whether phytate and oxalate interact via cross-linking by calcium and/or magnesium are also planned.
Progress concluded with the 2009 Annual Report for project 6435-13410-003-00D. See 2009 Annual Report for the last reported progress. Related work on phytase (enzyme that can break down the undigestible phytic acid (phytate) part found in grains oil seeds and thus release digestible phosphorus, calcium and other nutrients) is reported in the bridging project 6435-13410-004-00D. See 2010 Annual Report for 6435-13410-004-00D for the progress in FY-2010.