Enzyme kinetics - (Apr/03/2008 )

I want to determine the initial rate of reaction of an enzyme and measure the increase of amount of product over time.
I hoped to get a standard curve with a steep and linear slope followed by a plateau phase.
My enzyme shows a lag phase in the beginning of the reaction and a very flat slope. And I have to wait really long to reach the max. product amount value (which I determined in assays where I used larger amounts of enzyme and a higher specific activity of radiolabelled substrate).
Should I increase the amount of enzyme or the specific activity of my radiolabelled substrate to get a steeper slope and a standard-type curve?

Thanks for your help,

chalet2