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PubMed2003

Superior virological efficacy of ritonavir-boosted protease inhibitor regimens compared to single protease inhibitor therapy.

Low dose-ritonavir boosted protease inhibitors are increasingly being used for the first-line antiretroviral treatment, though their virological efficacy has just poorly been compared to alternative antiretroviral therapies. Here, we retrospectively investigated the virological responses of 316 protease inhibitor-naive HIV patients receiving highly active antiretroviral treatment based on a single (n = 256) or a ritonavir-boosted protease inhibitor (n = 60), both in the background of two nucleoside analogues. - By intent-to-treat analysis, a complete initial virological response was achieved in 71.8% of all patients in the single protease inhibitor group (indinavir: 76%, ritonavir: 67.5%, nelfinavir: 70.6%) and in 88.3% (p = 0.008) of patients treated with a boosted protease inhibitor (saquinavir/r: 71.4%, indinavir/r: 92.1%, lopinavir/r: 86.6%). The multivariate risk analysis identified boosted PI treatment as an independent predictor of a complete virological response (OR = 2.8, p=0.02). Viral rebound after an initial complete virological response was observed in 28% and 17% (p = 0.06) of patients receiving a single or a dual protease inhibitor, respectively. The rate of durable viral suppression over 12 months was 44.5% and 56.7% (p = 0.09) in the respective study cohorts. Ritonavir-boosted protease inhibitors therefore seem to induce a superior virological response rate and a higher degree of sustained virological suppression.

Adult↗
PubMed1978

Inhibition of platelet aggregation by protease inhibitors. Possible involvement of proteases in platelet aggregation.

The possible participation of proteases in human platelet aggregation was explored using various protease inhibitors and substrates. Protease inhibitors used included naturally occurring inhibitors of serine proteases and synthetic inhibitors that modify the active site of protease. Substrates used were synthetic substrates for the trypsin type as well as for the chymotrypsin type of protease. All these inhibitors and substrates inhibited platelet aggregation and serotonin release induced by ADP, collagen, epinephrine, or thrombin. In ADP- and epinephrine-induced platelet aggregation the second phase of aggregation was most efficiently inhibited. The inhibitors suppressed the formation of malondialdehyde during platelet aggregation. Release by aggregating agents of arachidonate and its metabolites from indomethacin-treated platelets as well as nontreated platelets was also inhibited. The inhibitors apperar to interact with stimulated platelets but not with unstimulated platelets. These observations suggest that the interaction of an aggregating agent with its platelet receptor activates a unique precursor serine protease that in turn activates platelet phospholipase to liberate arachidonic acid (the precursor of the potent platelet aggregating agent thromboxane A2) from platelet phospholipids.

Arachidonic Acids↗
PubMed1981

A new protease in hog thyroid lysosomes. I. The presence of a leupeptin-sensitive protease in the soluble fraction of thyroid lysosomes.

The presence of protease activity at pH 7.5 and at acidic pH was demonstrated in the soluble fraction of lysosomes which were prepared from hog thyroid homogenates by subcellular fractionation. The ratios of specific activity measured at pH 7.5 to that at pH 3.5 were 0.07 to 0.08 for casein (at pH 7.5) or haemoglobin (at pH 3.5) as substrate and 0.13 for iodoamino acid-releasing activity from thyroglobulin as substrate. The protease activity measured at pH 7.5 was inhibited by inhibitors for neutral type protease, such as leupeptin, and by sulfhydryl inhibitors, such as iodoacetamide, indicating that the protease was a leupeptin-sensitive protease and contained a sulfhydryl group for its active site. Insensitiveness of the protease activity to di-isopropyl fluorophosphate excluded the involvement of a serine group at the active site. At pH 5.5 the proteolytic and iodoamino acid-releasing activities using casein and thyroglobulin, respectively, were also investigated. Several lines of evidence suggested that both activities measured at pH 5.5 were due to a mixture of acidic and leupeptin-sensitive protease activities.

Animals↗
PubMed2001

Fibrinogenolytic proteases isolated from the snake venom of Taiwan habu: serine proteases with kallikrein-like and angiotensin-degrading activities.

Two venom proteases with fibrinogenolytic activity were isolated from the venom of Taiwan habu (Trimeresurus mucrosquamatus), one major crotalid snake species in Taiwan. The purified enzymes showed a strong beta-fibrinogenolytic activity, cleaving the beta-chain of fibrinogen molecules specifically. They also showed strong kallikrein-like activity in vitro, releasing bradykinin from kininogen. The purified enzymes did not coagulate human plasma, yet decreasing fibrinogen levels in plasma and prolonging bleeding without formation of fibrin clots, indicating that both proteases have specificities different from thrombin and the thrombin-like proteases of snake venom reported previously. They also exhibit amidase activity against N-benzoyl-Pro-Phe-Arg-p-nitroanilide, which is a specific synthetic substrate for kallikrein-like proteases. Their stability at high temperatures was examined and found to be more stable when compared with ancrod and thrombin. Intravenous injection of either protease was shown to lower blood pressure in experimental rats. Most noteworthy is the observation that the proteases can cleave angiotensin I and release bradykinin from plasma kininogen in vitro, which is a strong vasodilator and probably responsible for the in vivo hypotensive effect of these venom proteases.

Amino Acid Sequence↗
PubMed1995

Different evolutionary histories of kringle and protease domains in serine proteases: a typical example of domain evolution.

With the aim of elucidating the evolutionary processes of the kringle and protease domains in serine proteases which are involved with the system of blood coagulation and fibrinolysis, we constructed phylogenetic trees for the kringle and protease domains, separately, by use of amino acid sequence data. The phylogenetic trees constructed clearly showed that the topologies were different between the kringle and protease domains. Because both domains are coded by single peptides of serine proteases, this strongly suggests that the kringle and protease domains must have undergone different evolutionary processes. Thus, these observations imply that serine proteases evolve in a way such that each domain is a unit of evolution, exemplifying a typical mode of domain evolution. A possible relationship between the domain evolution and the exon shuffling theory is also discussed from the viewpoint of gene evolution.

Amino Acid Sequence↗
PubMed1995

A new alkaline serine protease from alkalophilic Bacillus sp.: cloning, sequencing, and characterization of an intracellular protease.

To obtain a new serine protease from alkalophilic Bacillus sp. NKS-21, shotgun cloning was carried out. As a result, a new protease gene was obtained. It encoded an intracellular serine protease (ISP-1) in which there was no signal sequence. The molecular weight was 34,624. The protease showed about 50% homology with those of intracellular serine proteases (ISP-1) from Bacillus subtilis, B. polymyxa, and alkalophilic Bacillus sp. No. 221. The amino acid residues that form the catalytic triad, Ser, His and Asp, were completely conserved in comparison with subtilisins (the extracellular proteases from Bacillus). The cloned intracellular protease was expressed in Escherichia coli, and its purification and characterization were carried out. The enzyme showed stability under alkaline condition at pH 10 and tolerance to surfactants. The cloned ISP-1 digested well nucleoproteins, clupein and salmin, for the substrates.

Amino Acid Sequence↗
PubMed1999

The protease activity of a calpain-like cysteine protease in Saccharomyces cerevisiae is required for alkaline adaptation and sporulation.

Abstract Saccharomyces cerevisiae has only one putative gene (designated CPL1) for a cysteine protease with a protease domain similar to that of calpain. This gene product shows significant sequence similarity to PalBp, a fungal (Emericella nidulans) calpain-like protease that is responsible for adaptation under alkaline conditions, both in the protease domain and the domain following the protease domain. CPL1 disruptant strains show impaired growth at alkaline pH, but no obvious growth defects under acidic pH conditions. This phenotype is complemented by the wild-type CPL1 gene, and its protease activity is essential for complementation. Disruption of CPL1 also causes reduced sporulation efficiency and promotes the degradation of the transcription factor Rim101p, which is involved in the sporulation pathway and has been shown to accumulate in a C-terminally truncated, active form under alkaline conditions. Furthermore, expression of the C-terminally truncated Rim101p suppressed the alkaline sensitivity associated with CPL1 disruption. These results indicate that a calpain-like cysteine protease, Cpl1p, plays an important role in alkaline adaptation and sporulation processes, via regulation of the turnover and processing of the transcription factor Rim101p.

Acid-Base Equilibrium↗
PubMed1986

Proteolysis of the calcium-dependent protease inhibitor by myocardial calcium-dependent protease.

Bovine heart peak II calcium-dependent protease was capable of hydrolyzing its specific inhibitor protein at high molar ratios of protease to inhibitor. The proteolysis was inhibited by leupeptin and required millimolar calcium. Thus, it appeared to be attributable to the calcium-dependent protease and not to possible contaminating proteases in the purified preparations of inhibitor or calcium-dependent protease. Incubation of the purified inhibitor with the calcium-dependent protease produced a discrete pattern of inhibitor fragments on Western blots developed with an inhibitor-specific monoclonal antibody. Traces of similar or identical lower molecular weight immunoreactive material could be observed in Western blots of bovine heart extracts, and the immunoreactivity present as these lower molecular weight forms could be increased by incubation of the extracts with calcium ion. These results suggest that the inhibitor can be proteolyzed to low molecular weight forms which can be detected in cardiac tissue extracts, and that calcium-dependent protease(s) may be responsible for this phenomenon.

Animals↗
PubMed1987

Multiple proteases from Streptomyces moderatus. I. Isolation and purification of five extracellular proteases.

The presence of multiple proteases in the culture filtrate of Streptomyces moderatus was detected. After preliminary purification by ammonium sulfate precipitation and decolorization using DEAE-cellulose, the fractionation of various proteases was carried out using CM-trisacryl cation-exchange chromatography. By this procedure, four different protease fractions (Fr.) were separated (Fr. I, II, III, and IV). The first fraction was further separated into two different proteolytically active fractions (Fr. IA and Fr. Ib) by DEAE-trisacryl anion-exchange chromatography. Fraction Ia was purified further by affinity chromatography on N-carbobenzoxy-D-phenylalanyl triethylenetetramine-Sepharose 4B. The second fraction (Fr. Ib) was purified by gel filtration on Ultrogel AcA 44. For the purification of the other protease fractions (Fr. II, III, and IV) single-step affinity chromatography methods were employed. Protease fractions II and III were purified by epsilon-aminocaproyl-4-(4-aminophenylazo)phenylarsonic acid Sepharose 4B and protease fraction IV was purified on epsilon-aminocaproyl trialanine-Sepharose 4B. All five proteases purified were found to be apparently homogeneous by gel electrophoretic methods.

Chromatography, DEAE-Cellulose↗
PubMed1981

A calcium-activated protease possibly involved in myofibrillar protein turnover. Isolation of a low-calcium-requiring form of the protease.

Two forms of calcium-activated neutral protease were isolated and purified from porcine skeletal muscle. The two forms of the protease differ markedly in their requirement for calcium with the low-calcium-requiring form showing one-half maximal activation at 45 micro M calcium while the high-calcium-requiring form shows one-half maximal activation at 0.74 micro M calcium. Additionally, they chromatograph differently on DEAE-cellulose, exhibit different mobilities in electrophoresis in a nondenaturing buffer, are affected differently by certain divalent cations, and have slightly different pH dependencies. Despite these differences, the purified forms of the calcium-activated protease co-chromatograph in gel permeation chromatography, have identical banding patterns on sodium dodecyl sulfate (SDS)-polyacrylamide gels, cross-react with an antibody directed against the 80 000-dalton subunit of the calcium-activated protease we originally purified from skeletal muscle (Dayton, W.R., Goll, D.E., Zeece, M.G., Robson, R.M. and Reville, W.J. (1976) Biochemistry 15, 2150-2158), and have identical effects on the ultrastructure of myofibrils. THe high-calcium-requiring protease purified in this study is very likely identical to the calcium-activated protease we originally purified from skeletal muscle. The properties of the low-calcium-requiring form of the protease suggest that it is the form of the enzyme that is active in vivo.

Animals↗
PubMed1992

Inhibition by acidic phospholipids of protein degradation by ER-60 protease, a novel cysteine protease, of endoplasmic reticulum.

A protein (ER60) with sequence similarity to phosphoinositide-specific phospholipase C-alpha purified from rat liver endoplasmic reticulum (ER) degraded ER resident proteins and is really a protease [(1992) J. Biol. Chem. 265, 15152-15159]. Therefore, ER60 is called ER-60 protease. We now show that negatively charged phospholipids, phosphatidylinositol, phosphatidylinositol 4,5-bisphosphate and phosphatidylserine inhibit ER protein degradation by ER-60 protease. Phosphatidylcholine and phosphatidylethanolamine show no effect on the activity of ER-60 protease. With the use of protease inhibitors, ER-60 protease is shown to be a novel cysteine protease distinct from those of the cytosol and lysosomes.

Amino Acid Sequence↗
PubMed1990

Thiol protease-thiol protease inhibitor imbalance in cardiac tissue of ageing cardiomyopathic hamsters.

In cardiomyopathic hamsters myofibrillar lesions and loss of muscle specific proteins occur in the heart early in life, and it has been suggested that intracellular proteases are involved in the process of muscle necrosis. In the age-dependent study reported here, we observed that cardiac tissue of dystrophic hamsters contains 30-100% more thiol protease activity than normal hamsters, with the greatest differences found in hearts of older animals. As well, the ratio of thiol protease activity in dystrophic hearts compared to normal hearts increases by 1.5-fold and 2.7-fold, respectively in the lysosomal and non-lysosomal fractions between 1.4 and 14 months of age. Cathepsin B accounted for over 90% of the thiol protease activity in the lysosomal fraction of both normal and dystrophic hamster hearts. In contrast, cardiac tissue of 3 to 14 month old dystrophic hamsters contains 20-45% less thiol protease inhibitor activity than hearts from age-matched normal hamsters. These results demonstrate that at an early age (1.4 to 3 months) an imbalance occurs between the thiol protease activity and thiol protease inhibitor content of cardiac tissue of dystrophic hamsters, which becomes more severe in older animals and associated with progressive myofibrillar lesions and tissue necrosis.

Aging↗
PubMed2002

Recombinant full-length human cytomegalovirus protease has lower activity than recombinant processed protease domain in purified enzyme and cell-based assays.

Herpesviruses encode a protease that is essential for virus replication. The protease undergoes cleavage to a processed form during capsid maturation. A recombinant 75 kDa form of the protease from human cytomegalovirus was purified and compared with the recombinant 29 kDa processed form. Modification with an active site titrant suggested that most of each recombinant protease preparation was active (66 and 86%, respectively). Protease activity was compared using a low-molecular weight peptide substrate and the native substrate, capsid assembly protein. In addition, a cell-based assay for both enzymes was developed in which the target sequence of the protease has been fused inframe into the herpes simplex virus VP16 molecule. Cleavage of the fusion protein by the protease releases the carboxyl terminal transactivation domain, resulting in a decrease in the ability of the fusion molecule to transactivate a target promoter linked to a reporter gene in mammalian cells. Results suggest that the 75 kDa form of the enzyme is significantly less active than the 29 kDa form by all criteria.

Amino Acid Sequence↗
PubMed1999

Evidence for the proenkephalin processing enzyme prohormone thiol protease (PTP) as a multicatalytic cysteine protease complex: activation by glutathione localized to secretory vesicles.

The cysteine protease known as "prohormone thiol protease" (PTP) has been identified as a major proenkephalin processing enzyme in secretory vesicles of adrenal medulla (known as chromaffin granules). This study provides the first demonstration that PTP exists as a multicatalytic cysteine protease complex that can be activated by endogenous glutathione present in chromaffin granules. The high molecular mass nature of PTP, of approximately 185 kDa, was demonstrated by elution of a single peak of 35S-enkephalin precursor cleaving activity by Sephacryl S200 gel filtration chromatography and by a single band of 35S-enkephalin precursor cleaving activity detected on radiozymogram gels under native buffer conditions. Importantly, when 0.1% SDS was included in radiozymogram gels, PTP activity was resolved into three bands of proteolytic activity with apparent molecular masses of 88, 81, and 61 kDa. These activities were all cysteine proteases, since they were inhibited by the cysteine protease inhibitor E-64c but not by pepstatin A or EDTA that inhibit aspartyl protease and metalloprotease, respectively. Purification of native PTP by preparative gel electrophoresis indicated that PTP was composed of four polypeptides of 66, 60, 33, and 29 kDa detected on SDS-PAGE gels. These four protein subunits accounted for the three catalytic activities of PTP, as demonstrated on 35S-enkephalin precursor radiozymogram gels. Results also indicated that the electrophoretic mobilities of the four subunits differed under reducing compared to nonreducing conditions. The multicatalytic activities of the PTP complex all require reducing conditions for activity, which can be provided by endogenous reduced glutathione in chromaffin granules. These novel findings provide the first evidence for a role of a multicatalytic cysteine protease complex, PTP, in chromaffin granules that may be involved in the proteolytic processing of proenkephalin and perhaps other precursors into active neuropeptides.

Amino Acid Sequence↗
PubMed1999

Membrane-protease interactions. III: A consideration of the difference in binding potential of pancreatic proteases to erythrocytes and erythrocyte ghosts.

Trypsin and chymotrypsin readily bind to human erythrocyte ghosts and to resealed right-side-out ghosts, but not to intact erythrocytes, as followed with [3H]trypsin and [3H]chymotrypsin and with cold proteases in a caseinolytic assay. The proteases freely reacted with casein in the presence of intact cells. Trypsin activated trypsinogen over an 8-hr time course at a faster rate in the presence of erythrocytes than in the absence thereof, after a slight initial delay. Trypsinogen did not bind to intact erythrocytes, thereby behaving comparably to trypsin. These results suggest that different microenvironments exist about the erythrocyte ghosts and the intact erythrocytes, thereby permitting the proteases to bind to the former but not to the latter. Hence, in the absence of considerable ghosts in circulating blood, which may mask the binding site of the proteases, the proteases may be more readily accessible for interaction with circulating serpins, leading to inactivation of the proteases and protection from their degradative potential. The presence of the serpins in circulating blood may assist in the control of the degradative power of the pancreatic proteases in pancreatitis and may negatively modulate such processes as thrombosis, activation of the complement system, and vascular remodeling.

Binding, Competitive↗
PubMed1996

A new serine-protease fold revealed by the crystal structure of human cytomegalovirus protease.

Human cytomegalovirus (hCMV), a herpesvirus, infects up to 70% of the general population in the United States and can cause morbidity and mortality in immunosuppressed individuals (organ-transplant recipients and AIDS patients) and congenitally infected newborns. hCMV protease is essential for the production of mature infectious virions, as it performs proteolytic processing near the carboxy terminus (M-site) of the viral assembly protein precursor. hCMV protease is a serine protease, although it has little homology to other clans of serine proteases. Here we report the crystal structure of hCMV protease at 2.0 angstroms resolution, and show that it possesses a new polypeptide backbone fold. Ser 132 and His 63 are found in close proximity in the active site, confirming earlier biochemical and mutagenesis studies. The structure suggests that the third member of the triad is probably His 157. A dimer of the protease with an extensive interface is found in the crystal structure. This structure information will help in the design and optimization of inhibitors against herpesvirus proteases.

Crystallography, X-Ray↗
PubMed1981

The product of the lon (capR) gene in Escherichia coli is the ATP-dependent protease, protease La.

In Escherichia coli, degradation of abnormal proteins is an energy-requiring process; it is decreased in mutants in the lon (capR or deg) gene. We find that the protein encoded by the lon gene is an ATP-dependent protease and is identical to protease La, recently described in E. coli. Both proteins are serine proteases that hydrolyze casein and globin, but not insulin, in the presence of ATP and Mg2+. Both respond to ATP, less well to other nucleoside triphosphates, and not to nonhydrolyzable ATP analogs. The purified lon protein has an apparent Mr of 450,000 and appears to be composed of four identical subunits. Its size, chromatographic behavior, and sensitivity to various inhibitors and heat are indistinguishable from those of protease La. Moreover, in a strain that carries additional copies of the lon+ allele on a plasmid, the content of protease La, but not of other proteases, is 2- to 10-fold greater than in the lon+ parent strain. Strains carrying the nonsense mutations capR9 and capR- also contain this ATP-dependent proteolytic activity, but it is present in substantially lower amounts and is inactivated by phosphocellulose chromatography, unlike the wild-type enzyme. Degradation of abnormal proteins in these lon- strains, which is slower than in the wild type, still requires ATP. Alterations in the ATP-dependent protease in the lon- mutants can account for the defect in intracellular proteolysis and perhaps also for the other phenotypic effects of this pleiotropic gene.

Adenosine Triphosphatases↗
PubMed2005

A Second Kazal-like protease inhibitor from Phytophthora infestans inhibits and interacts with the apoplastic pathogenesis-related protease P69B of tomato.

The plant apoplast forms a protease-rich environment in which proteases are integral components of the plant defense response. Plant pathogenic oomycetes, such as the potato (Solanum tuberosum) and tomato (Lycopersicon esculentum) pathogen Phytophthora infestans, secrete a diverse family of serine protease inhibitors of the Kazal family. Among these, the two-domain EPI1 protein was shown to inhibit and interact with the pathogenesis-related protein P69B subtilase of tomato and was implicated in counter-defense. Here, we describe and functionally characterize a second extracellular protease inhibitor, EPI10, from P. infestans. EPI10 contains three Kazal-like domains, one of which was predicted to be an efficient inhibitor of subtilisin A by an additivity-based sequence to reactivity algorithm (Laskowski algorithm). The epi10 gene was up-regulated during infection of tomato, suggesting a potential role during pathogenesis. Recombinant EPI10 specifically inhibited subtilisin A among the major serine proteases, and inhibited and interacted with P69B subtilase of tomato. The finding that P. infestans evolved two distinct and structurally divergent protease inhibitors to target the same plant protease suggests that inhibition of P69B could be an important infection mechanism for this pathogen.

Amino Acid Sequence↗