TABLE 1.

Characteristics of human Kunitz protease inhibitor domains

Kunitz domain	MEROPS ID	Gene	UNIPROT ID	aa position in precursora	P1 residue	Reported Ki for trypsin inhibition
						m
APPI	I02.015	APP	P05067	287–344	Arg	1.7 × 10−10b (15); 3.1 × 10−10c (54)
APLP2-KD	I02.016	APLP2	Q06481	306–363	Arg	3.2 × 10−10c (55)
Bikunin-KD2	I02.006	AMBP	P02760	283–340	Arg	2.5 × 10−8b; 1.3 × 10−10d (35)
HAI1-KD1	I02.007	SPINT1	O43278	246–303	Arg	2.4 × 10−9c (34)
HAI1-KD2	I02.008	SPINT1	O43278	387–444	Lys	>2 × 10−7c (34)
HAI2-KD1	I02.009	SPINT2	O43291	34–91	Arg	3 × 10−11c (66)
HAI2-KD2	I02.0010	SPINT2	O43291	129–186	Arg	5 × 10−11c (66)
TFPI1-KD1	I02.0011	TFPI	P10646	50–107	Lys	1.2 × 10−8d (83)
TFPI1-KD2	I02.0012	TFPI	P10646	121–178	Arg	1 × 10−10d (83)
TFPI2-KD1	I02.0013	TFPI2	P48307	32–89	Arg	1.3 × 10−8d (84)
WFIKKN1-KD2	I02.0033	WFIKKN1	Q96NZ8	355–412	Arg	9.6 × 10−9c (85)

^a aa, amino acid; Kunitz domain boundaries here were defined to include 4 residues preceding the initial Cys residue and 3 residues following that sixth/final Cys residue for consistency.

^b Measured versus human cationic trypsin.

^c Measured versus bovine trypsin.

^d Measured versus porcine trypsin.