thrombin source for fusion prot cleav.

[GLUXLAB]

Protein People:
	We are currently using highly purified human thrombin 
4,000 Units/mg [sigma #T-3010] for cleaving our fused protein 
from glutathione S transferase.  the price is becoming 
prohibitive ~$300/1000 units. is there a better source for
thrombin, and not neccessarily human that will work as well.
our end product id being crystallized for structure determination
as well as for nmr characterization.

thanks,

laurette