Defining Phytase Units

Phytase Enzyme Units

Are an in vitro measure used to certify activity in a given product form, i.e., required for labeling.
In vitro units do not equal in vivo bio-activity of an enzyme.
Can be affected by fermentation conditions, purification steps and formulation of final product forms.
Can be affected by assay conditions and the reagents utilized.
Phytase units have become a source of confusion in today’s market.

RONOZYME® P Units: FYT (DSM)
Natuphos Units: FTU (BASF)
Optiphos Units: FTU (Enzyvia/JBS United)
Phyzyme Units: FTU (Danisco)
- Amount of enzyme that catalyzes the release of 1 µMol of Pi per minute from 5.1 mM sodium phytate in pH 5.5 buffer at 37° C
Quantum Unit, QPU (AB Vista)
- Amount of enzyme that catalyzes the release of 1 µMol of Pi per minute from 5.1 mM sodium phytate in pH 4.5 buffer at 60° C

Amount of enzyme that catalyzes the release of 1 µMol of Pi per minute from 5.1 mM sodium phytate in pH 5.5 buffer at 37° C
Same definition used for all 4 major commercial phytases in NAA yet analytical procedures are different

Extraction
- Solubilize phytase activity within sample into aqueous phase
Incubation
- Reaction of phytase unknown (aliqout of extraction solution) with a standard concentration of substrate (sodium phytate).
- Addition of color reactants with stopping solution for enzyme reaction
Quantification of Phosphorus
- Determine levels of phosphorus released in incubation phase (corrected for background phosphorus in feed)
Determine Phytase Units/kg feed
- Divide micromoles Pi released by incubation time and sample weight

Amount of enzyme that catalyzes the release of 1 µMol of Pi per minute from 5.1 mM sodium phytate in pH 5.5 buffer at 37° C