If you know have your protein sequence, go for protparam and see the parameters

which includes Pi,stability index etc.........

Hi Ramray,

if you know the primary structure of your enzyme you can use theoretical PI calculator from ExPASy: http://web.expasy.org/compute_pi/

The real PI might differ in reality, but it always worked fine for me.

Best

Kai

For the real IP, use an isoelectric focusing gel. A calculated IP is probably good enough to set up an ion exchange column

incubate your enzyme at different pHs then incubate at -15 degree centigrate for 2 days then do ultracentrifugation. decantate the supernatant then measure the protein content for all . the pH at which maximum protein content attained is pI. this is the simplest and cheapest method

you can also use

1. IPG strips

isoeclecric focusing gel (the most common)

E Kotb