The amino acid sequence of a Bowman-Birk type proteinase inhibitor from faba beans (Vicia faba L.).

The amino acid sequence of a Bowman-Birk type proteinase inhibitor (FBI) from seeds of faba bean (Vicia faba L.) was determined by analysis of peptide fragments generated by reduction and S-carboxymethylation of enzymatically modified inhibitors, which were obtained from native FBI by limited proteolysis with TPCK-trypsin or TLCK-chymotrypsin at pH 3.5. The established sequence showed that FBI is highly homologous with Vicia angustifolia inhibitor (VAI0 but lacks the portion corresponding to the C-terminal 9 amino acids of VAI. The trypsin reactive-site peptide bond in FBI was also indicated to be Lys(16)-Ser(17) and the chymotrypsin reactive-site peptide bond to be Tyr(42)-Ser(43) by limited proteolysis with TPCK-trypsin or TLCK-chymotrypsin and by sequence comparison with other Bowman-Birk type inhibitors.     

Purification and amino acid sequence of a bitter gourd inhibitor against an acidic amino acid-specific endopeptidase of Streptomyces griseus.

An inhibitor (BGIA) against an acidic amino acid-specific endopeptidase of Streptomyces griseus (Glu S. griseus protease) was isolated from seeds of the bitter gourd Momordica charantia L., and its amino acid sequence was determined. The molecular weight of BGIA based on the amino acid sequence was calculated to be 7419. BGIA competitively inhibited Glu S. griseus protease with an inhibition constant (Ki) of 70 nM, and gel filtration analyses suggested that BGIA forms a 1:1 complex with this protease. However, two other acidic amino acid-specific endopeptidases, protease V8 from Staphylococcus aureus and Bacillus subtilis proteinase (Glu B. subtilis protease), were not inhibited by BGIA. BGIA had no inhibitory activity against chymotrypsin, trypsin, porcine pancreatic elastase, and papain, although subtilisin Carlsberg was strongly inhibited. The amino acid sequence of BGIA shows similarity to potato chymotrypsin inhibitor, barley subtilisin-chymotrypsin inhibitor CI-1 and CI-2, and leech eglin C, especially around the reactive site. Although the residue at the putative reactive site of these inhibitors is leucine or methionine, the corresponding amino acid in BGIA is alanine.     

Incorporation of Streptidine-C6-phosphate into Phosphorylated Streptomycin by Resting Cell of Streptomyces griseus

The Kunitz-type trypsin inhibitors, ETIa and ETIb, and chymotrypsin inhibitor ECI were isolated from the seeds of Erythrina variegata. The proteins were extracted from a defatted meal of seeds with 10 mM phosphate buffer, pH 7.2, containing 0.15 M NaCl, and purified by DEAE-cellulose and Q-Sepharose column chromatographies. The stoichiometry of trypsin inhibitors with trypsin was estimated to be 1:1, while that of chymotrypsin inhibitor with chymotrypsin was 1:2, judging from the titration patterns of their inhibitory activities.

The complete amino acids of the two trypsin inhibitors were sequenced by protein chemical methods. The proteins ETIa and ETIb consist of 172 and 176 amino acid residues and have M_r 19,242 and M_r 19,783, respectively, and share 112 identical amino acid residues, which is 65% identity. They show structural features characteristic of the Kunitz-type trypsin inhibitor (i.e., identical residues at about 45%) with soybean trypsin inhibitor STI). Furthermore, the trypsin inhibitors show a significant homology to the storage proteins, sporamin, in sweet potato and the taste-modifying protein, miraculin, in miracle fruit, having about 30% identical residues.     

The complete amino acid sequence of the major Kunitz trypsin inhibitor from the seeds of Prosopsis juliflora.

The major inhibitor of trypsin in seeds of Prosopsis juliflora was purified by precipitation with ammonium sulphate, ion-exchange column chromatography on DEAE- and CM-Sepharose and preparative reverse phase HPLC on a Vydac C-18 column. The protein inhibited trypsin in the stoichiometric ratio of 1:1, but had only weak activity against chymotrypsin and did not inhibit human salivary or porcine pancreatic alpha-amylases. SDS-PAGE indicated that the inhibitor has a Mr of ca 20,000, and IEF-PAGE showed that the pI is 8.8. The complete amino acid sequence was determined by automatic degradation, and by DABITC/PITC microsequence analysis of peptides obtained from enzyme digestions of the reduced and S-carboxymethylated protein with trypsin, chymotrypsin, elastase, the Glu-specific protease from S. aureus and the Lys-specific protease from Lysobacter enzymogenes. The inhibitor consisted of two polypeptide chains, of 137 residues (alpha chain) and 38 residues (beta chain) linked together by a single disulphide bond. The amino acid sequence of the protein exhibited homology with a number of Kunitz proteinase inhibitors from other legume seeds, the bifunctional subtilisin/alpha-amylase inhibitors from cereals and the taste-modifying protein miraculin.     

Amino acid sequence of the acidic Kunitz-type trypsin inhibitor from winged-bean seed [Psophocarpus tetragonolobus (L.) DC]

The primary sequence of trypsin inhibitor-2 (WBTI-2) fromPsophocarpus tetragonolobus (L.) DC seeds was determined. This inhibitor consists of a single polypeptide chain of 182 amino acids, including four half-cystine residues, and an N-terminal residue of pyroglutamic acid. The sequence of WBTI-2 showed 57% identity to the basic trypsin inhibitor (WBTI-3) and 50% identity to the chymotrypsin inhibitor (WBCI) of winged bean, and 54% identity to the trypsin inhibitor DE-3 fromErythrina latissima seed. The similarity to the soybean Kunitz trypsin inhibitor (40%) and the other Kunitz-type inhibitors fromAdenanthera pavonina (30%) and wheat (26%) was much lower. Sequence comparisons indicate that thePsophocarpus andErythrina inhibitors are more closely related to each other than to other members of the Kunitz inhibitor family.     

Purification,amino acid sequence,and cDNA cloning of trypsin inhibitors from onion (Allium cepa L.) bulbs

Three protease inhibitors (OTI-1-3) have been purified from onion (Allium cepa L.) bulbs. Molecular masses of these inhibitors were found to be 7,370.2, 7,472.2, and 7,642.6 Da by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), respectively. Based on amino acid composition and N-terminal sequence, OTI-1 and -2 are the N-terminal truncated proteins of OTI-3. All the inhibitors are stable to heat and extreme pH. OTI-3 inhibited trypsin, chymotrypsin, and plasmin with dissociation constants of 1.3 x 10(-9) M, 2.3 x 10(-7) M, and 3.1 x 10(-7) M, respectively. The complete amino acid sequence of OTI-3 showed a significant homology to Bowman-Birk family inhibitors, and the first reactive site (P1) was found to be Arg17 by limited proteolysis by trypsin. The second reactive site (P1) was estimated to be Leu46, that may inhibit chymotrypsin. OTI-3 lacks an S-S bond near the second reactive site, resulting in a low affinity for the enzyme. The sequence of OTI-3 was also ascertained by the nucleotide sequence of a cDNA clone encoding a 101-residue precursor of the onion inhibitor.     

A specific inhibitor of Colletotrichum lindemuthianum protease from kidney bean (Phaseolus vulgaris) seeds

A specific protein—an inhibitor of Colletotrichum lindemuthianum protease—was isolated from kidney bean seeds in a homogeneous form. The purification procedure included gel filtration, isoelectric focusing and affinity chromatography on trypsin-Sepharose column. The latter was introduced to separate the fungal protease inhibitor from closely related trypsin and chymotrypsin inhibitors present in kidney bean seeds.     

Isolation and primary structure of proteinase inhibitors from Erythrina variegata (Linn.) var. Orientalis seeds.

The Kunitz-type trypsin inhibitors, ETIa and ETIb, and chymotrypsin inhibitor ECI were isolated from the seeds of Erythrina variegata. The proteins were extracted from a defatted meal of seeds with 10 mM phosphate buffer, pH 7.2, containing 0.15 M NaCl, and purified by DEAE-cellulose and Q-Sepharose column chromatographies. The stoichiometry of trypsin inhibitors with trypsin was estimated to be 1:1, while that of chymotrypsin inhibitor with chymotrypsin was 1:2, judging from the titration patterns of their inhibitory activities. The complete amino acids of the two trypsin inhibitors were sequenced by protein chemical methods. The proteins ETIa and ETIb consist of 172 and 176 amino acid residues and have M(r) 19,242 and M(r) 19,783, respectively, and share 112 identical amino acid residues, which is 65% identity. They show structural features characteristic of the Kunitz-type trypsin inhibitor (i.e., identical residues at about 45% with soybean trypsin inhibitor STI). Furthermore, the trypsin inhibitors show a significant homology to the storage proteins, sporamin, in sweet potato and the taste-modifying protein, miraculin, in miracle fruit, having about 30% identical residues.     

Plant Growth Retarding Activity of the 4-Substituted-7-(β-d-ribofuranosyl)pyrrolo[2,3-d]pyrimidine Anticytokinins

Three protease inhibitors (OTI-1-3) have been purified from onion (Allium cepa L.) bulbs. Molecular masses of these inhibitors were found to be 7,370.2, 7,472.2, and 7,642.6 Da by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), respectively. Based on amino acid composition and N-terminal sequence, OTI-1 and -2 are the N-terminal truncated proteins of OTI-3. All the inhibitors are stable to heat and extreme pH. OTI-3 inhibited trypsin, chymotrypsin, and plasmin with dissociation constants of 1.3×10^-9 M, 2.3×10^-7 M, and 3.1×10^-7 M, respectively. The complete amino acid sequence of OTI-3 showed a significant homology to Bowman-Birk family inhibitors, and the first reactive site (P₁) was found to be Arg¹⁷ by limited proteolysis by trypsin. The second reactive site (P₁) was estimated to be Leu⁴⁶, that may inhibit chymotrypsin. OTI-3 lacks an S-S bond near the second reactive site, resulting in a low affinity for the enzyme. The sequence of OTI-3 was also ascertained by the nucleotide sequence of a cDNA clone encoding a 101-residue precursor of the onion inhibitor.     

The amino acid sequence of a cereal Bowman-Birk type trypsin inhibitor from seeds of Jobs' tears (Coix lachryma-jobi L.)

The major trypsin inhibitor from seeds of Jobs' tears (Coix lachryma-jobi) was purified by heat treatment, fractional precipitation with (NH4)2SO4, ion-exchange chromatography on DEAE-Sepharose, gel-filtration on Sephadex G-75 and preparative reverse-phase HPLC. The complete amino acid sequence was determined by analysis of peptides derived from the reduced and S-carboxymethylated protein by digestion with trypsin, chymotrypsin and the S. aureus V8 protease. The polypeptide contained 64 amino acids with a high content of cysteine. The sequence exhibited strong homology with a number of Bowman-Birk inhibitors from legume seeds and similar proteins recently isolated from wheat and rice.     

The Complete Amino Acid Sequence of a Trypsin Inhibitor from Bauhinia variegata var. candida Seeds

Trypsin inhibitors of two varieties of Bauhinia variegata seeds have been isolated and characterized. Bauhinia variegata candida trypsin inhibitor (BvcTI) and B. variegata lilac trypsin inhibitor (BvlTI) are proteins with M _r of about 20,000 without free sulfhydryl groups. Amino acid analysis shows a high content of aspartic acid, glutamic acid, serine, and glycine, and a low content of histidine, tyrosine, methionine, and lysine in both inhibitors. Isoelectric focusing for both varieties detected three isoforms (pI 4.85, 5.00, and 5.15), which were resolved by HPLC procedure. The trypsin inhibitors show K _i values of 6.9 and 1.2 nM for BvcTI and BvlTI, respectively. The N-terminal sequences of the three trypsin inhibitor isoforms from both varieties of Bauhinia variegata and the complete amino acid sequence of B. variegata var. candida L. trypsin inhibitor isoform 3 (BvcTI-3) are presented. The sequences have been determined by automated Edman degradation of the reduced and carboxymethylated proteins of the peptides resulting from Staphylococcus aureus protease and trypsin digestion. BvcTI-3 is composed of 167 residues and has a calculated molecular mass of 18,529. Homology studies with other trypsin inhibitors show that BvcTI-3 belongs to the Kunitz family. The putative active site encompasses Arg (63)–Ile (64).     

Purification and characterization of a proteinase inhibitor from field bean, Dolichos lablab perpureus L

A proteinase inhibitor resembling Bowman-Birk family inhibitors has been purified from the seeds of cultivar HA-3 of Dolichos lablab perpureus L. The protein was apparently homogeneous as judged by SDS–PAGE, PAGE, IEF, and immunodiffusion. The inhibitor had 12 mole% 1/2-cystine and a few aromatic amino acids, and lacks tryptophan. Field bean proteinase inhibitor (FBPI) exhibited a pI of 4.3 and an M _r of 18,500 Da. CD spectral studies showed random coiled secondary structure. Conformational changes were detected in the FBPI–trypsin/chymotrypsin complexes by difference spectral studies. Apparent K _a values of complexes of inhibitor with trypsin and chymotrypsin were 2.1 × 10⁷ M^–1 and 3.1 × 10⁷ M^–1, respectively. The binary and ternary complexes of FBPI with trypsin and chymotrypsin have been isolated indicating 1:1 stoichiometry with independent sites for cognate enzymes. Amino acid modification studies showed lysine and tyrosine at the reactive sites of FBPI for trypsin and chymotrypsin, respectively.     

Purification and characterization of proteinase inhibitors from adzuki beans (Phaseolus angularis).

Two proteinase inhibitors, designated as inhibitors I and II, were purified from adzuki beans (Phaseolus angularis) by chromatographies on DEAE- and CM-cellulose, and gel filtration on a Sephadex G-100 column. Each inhibitor shows unique inhibitory activities. Inhibitor I was a powerful inhibitor of trypsin [EC 3.4.21.4], but essentially not of chymotrypsin ]EC 3.4.21.1]. On the other hand, inhibitor II inhibited chymotrypsin more strongly than trypsin. The molecular weights estimated from the enzyme inhibition were 3,750 and 9,700 for inhibitors I and II, respectively, assuming that the inhibitions were stoichiometric and in 1 : 1 molar ratio. The amino acid compositions of both inhibitors closely resemble those of low molecular weight inhibitors of other leguminous seeds: they contain large amounts of half-cystine, aspartic acid and serine, and little or no hydrophobic and aromatic amino acids. Inhibitor I lacks both tyrosine and tryptophan residues. The molecular weights were calculated to be 7,894 and 8,620 for inhibitors I and II, respectively. The reliability of these molecular weights was confirmed by the sedimentation equilibrium and 6 M guanidine gel filtration methods. On comparison with the values obtained from enzyme inhibition, it was concluded that inhibitor I and two trypsin inhibitory sites on the molecule, whereas inhibitor II had one chymotrypsin and one trypsin inhibitory sites on the molecule.     

Purification and characterization of a trypsin inhibitor from seeds of Murraya koenigii

A protein with trypsin inhibitory activity was purified to homogeneity from the seeds of Murraya koenigii (curry leaf tree) by ion exchange chromatography and gel filtration chromatography on HPLC. The molecular mass of the protein was determined to be 27 kDa by SDS-PAGE analysis under reducing conditions. The solubility studies at different pH conditions showed that it is completely soluble at and above pH 7.5 and slowly precipitates below this pH at a protein concentration of 1 mg/ml. The purified protein inhibited bovine pancreatic trypsin completely in a molar ratio of 1:1.1. Maximum inhibition was observed at pH 8.0. Kinetic studies showed that Murraya koenigii trypsin inhibitor is a competitive inhibitor with an equilibrium dissociation constant of 7 × 10^{? 9} M. The N-terminal sequence of the first 15 amino acids showed no similarity with any of the known trypsin inhibitors, however, a short sequence search showed significant homology to a Kunitz-type chymotrypsin inhibitor from Erythrina variegata.     

Properties of purified gut trypsin from Helicoverpa zea, adapted to proteinase inhibitors.

Pest insects such as Helicoverpa spp. frequently feed on plants expressing protease inhibitors. Apparently, their digestive system can adapt to the presence of protease inhibitors. To study this, a trypsin enzyme was purified from the gut of insects that were raised on an inhibitor-containing diet. The amino-acid sequence of this enzyme was analysed by tandem MS, which allowed assignment of 66% of the mature protein amino acid sequence. This trypsin, called HzTrypsin-S, corresponded to a known cDNA sequence from Helicoverpa. The amino acid sequence is closely related (76% identical) to that of a trypsin, HzTrypsin-C, which was purified and identified in a similar way from insects raised on a diet without additional inhibitor. The digestive properties of HzTrypsin-S and HzTrypsin-C were compared. Both trypsins appeared to be equally efficient in degrading protein. Four typical plant inhibitors were tested in enzymatic measurements. HzTrypsin-S could not be inhibited by > 1000-fold molar excess of any of these. The same inhibitors inhibited HzTrypsin-C with apparent equilibrium dissociation constants ranging from 1 nm to 30 nm. Thus, HzTrypsin-S seems to allow the insect to overcome different defensive proteinase inhibitors in plants.     

First report on a potato I family chymotrypsin inhibitor from the seeds of a Cucurbitaceous plant, Momordica cochinchinensis

A 7514-Da chymotrypsin inhibitor was isolated from the seed extract of Momordica cochinchinensis (Family Cucurbitaceae) by chromatography on chymotrypsin-Sepharose 4B and subsequently by C18 reversed-phase HPLC. This inhibitor, named MCoCl, possessed remarkable thermostability and was stable from pH 2 to 12. MCoCl also inhibited subtilisin, but had at least 50-fold lower inhibitory activity towards trypsin and elastase. Amino acid sequencing of a peptide fragment of MCoCl revealed a sequence of 23 amino acids. Comparison of this sequence and the molecular mass with those of other protease inhibitors suggests that MCoCl belongs to the potato I inhibitor family.     

Purification, characterization and primary structure of a chymotrypsin inhibitor from Naja atra venom

A chymotrypsin inhibitor, designated NA-CI, was isolated from the venom of the Chinese cobra Naja atra by three-step chromatography. It inhibited bovine alpha-chymotrypsin with a Ki of 25 nM. The molecular mass of NA-CI was determined to be 6403.8 Da by matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) analysis. The complete amino acid sequence was determined after digestion of S-carboxymethylated inhibitor with Staphylococcus aureus V8 protease and porcine trypsin. NA-CI was a single polypeptide chain composed of 57 amino acid residues. The main contact site with the protease (P1) has a Phe, showing the specificity of the inhibitor. NA-CI shared great similarity with the chymotrypsin inhibitor from Naja naja venom (identities=89.5%) and other snake venom protease inhibitors.     

The effect of variation within inhibitory domains on the activity of pea protease inhibitors from the Bowman-Birk class

We have investigated the properties of variant pea seed protease inhibitors, homologous to the anti-carcinogenic Bowman-Birk inhibitor (BBI) from soybean but differing most significantly in amino acid sequences at the two independent sites of protease inhibition. The pea protease inhibitors were expressed, using Aspergillus niger, with yields of up to 23 mg secreted recombinant protein per litre of media. The recombinant proteins showed protease inhibitory activity and were deduced to be disulphide-bonded correctly; limited post-translational processing had occurred at the amino-terminal ends of all proteins. Differences in trypsin and chymotrypsin specific inhibitory activities, and in inhibition constants, were observed in studies of the two recombinant variants and BBI.     

Sequence of a new Bowman-Birk inhibitor fromTorresea acreana seeds and comparison withTorresea cearensis trypsin inhibitor (TcTI2)

TaTI (Torresea acreana trypsin inhibitor), a new member of the Bowman-Birk trypsin inhibitor family, was purified from seeds ofTorresea acreana, one of the two known species ofTorresea, a Brazilian native Leguminosae of the Papilionoideae subfamily. Purification was performed by acetone fractionation, anion-exchange chromatography, and gel filtration. The TaTI appears asM _r 7000 in SDS-PAGE under reducing conditions. There are 63 amino acid residues present in the TaTI sequence, which was confirmed by mass spectrometry (8388 daltons). The putative reactive sites residues were Lys-15 and Arg-42 at the first and second site, respectively. The antibodies raised against TcTI2,Torresea cearensis trypsin inhibitor 2, showed a cross-reaction with TaTI, but not with other Bowman-Birk inhibitors purified from Leguminosae. The inhibition constants of TaTI and TcTI2 were comparable when measured against trypsin, chymotrypsin, and factor XIIa, but not on plasmin. The latter was tenfold more effectively inhibited by TcTI2 then by TaTI. Neither TaTI nor TcTI2 affects thrombin, plasma kallikrein, or factor Xa.     

The complete amino acid sequence of trypsin inhibitor DE-3 from Erythrina latissima seeds

Trypsin inhibitor DE-3 from Erythrina latissima seeds contains 172 amino acids, including 4 half-cystine residues, and resembles the Kunitz-type inhibitors. Limited hydrolysis of DE-3 with trypsin at pH 3 produced two fragments, F1 and F2, containing 63 and 109 amino acids, respectively. Amino-terminal sequence studies revealed that F1 was the N-terminal and that F2 was the C-terminal fragment. The complete amino acid sequence of fragments F1 and F2 was then determined on peptides produced by enzymatic digestion with trypsin and Staphylococcus aureus V8 protease. The sequence of trypsin inhibitor DE-3 from E. latissima seeds shows a high degree of homology to those of Kunitz-type trypsin inhibitors from soybeans and winged bean seeds.