William Tivol tivol at
Thu Jan 18 12:56:18 EST 1996

S J Holton (S.J.Holton at wrote:
: Could somebody tell me whether pancreatic trypsin inhibitor is the same, 
: or a structural analogue of benzamidine hydrochloride?  Do either of 
: these inhibit trypsin by competitive inhibition?

Dear Simon,
	Pancreatic trypsin inhibitor is a protein which contains an amino
acid sequence which binds tightly to trypsin, but which is not cleaved due
to stabilization of the intermediate state in the enzyme-inhibitor complex.
Benzamidine is C6H5C(=NH)NH2--a benzine with a NHCNH2 group substituted for
one of the H--and the hydrochloride is C6H5C(NH2)2+ Cl-.  PTI is a competa-
tive inhibitor (with a similar "on rate" as substrate, but a *much* slower
"off rate"); I do not know the mechanism of inhibition of benzamidine.
				Bill Tivol

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