Crystallization and preliminary X-ray analysis of the ternary complex of procarboxypeptidase A from bovine pancreas

The ternary complex of procarboxypeptidase A, chymotrypsinogen C and proproteinase E from bovine pancreas has been crystallized using the sitting drop vapour diffusion method. The success in obtaining crystals has been found to be critically dependent on the prevention of autolysis of the complex. In preliminary stages, crystals twinned by merohedry were obtained from a solution containing MgCl2 and polyethylenglycol 400 as precipitating agent. Later on, untwinned ones could be grown employing CaCl2 instead of MgCl2. These latter crystals belong to the rhombohedral system and to the spacegroup R3 with cell dimensions a = b = 188.5 A and c = 82.5 A. Consideration of the possible values of Vm accounts for the presence of one ternary complex molecule-oligomere per asymmetric unit. The crystals diffract beyond 2.6 A resolution and are suitable for X-ray analysis.

A tumor necrosis factor-beta polymorphism associated with hypertriglyceridemia in non-insulin-dependent diabetes mellitus

Non-insulin-dependent (type II) diabetes mellitus is associated with significant abnormalities of lipoprotein metabolism. Control of glycemia rarely completely corrects the alterations in lipid metabolism, suggesting a participation of environmental and genetic factors. The observation that tumor necrosis factor (TNF) can modulate triglyceride metabolism offers a new genetic candidate to be analyzed. Samples of DNA from 91 control subjects and 61 diet-treated type II diabetic patients were analyzed to determine the lipid profile and a possible association with TNF genetic polymorphisms. For TNF restriction fragment length polymorphisms, we used the Nco I restriction enzyme and a TNF-alpha probe obtaining two allelic bands at 10.5 and 5.5 kb. We found a significant association (P < .01) of the 10.5-kb homozygous genotype in type II diabetic subjects with high triglyceride levels. Furthermore, these patients showed significant differences in triglycerides as compared with matched control subjects with the same genotype (P < .001). This study provides support for considering the TNF locus as a susceptibility genetic region in the hypertriglyceridemia of type II diabetes.

The sequence and conformation of human pancreatic procarboxypeptidase A2. cDNA cloning, sequence analysis, and three-dimensional model

A full-length cDNA clone coding for human pancreatic preprocarboxypeptidase A2 has been isolated from a lambda gt 11 human pancreatic library. Expression clones were identified by specific interaction with antisera raised against the native protein. The open reading frame of the polynucleotide sequence is 1254 base pairs in length and encodes a protein of 417 amino acids. This cDNA includes a short leader signal peptide of 16 amino acids and a 94-amino acid-long activation segment. The amino acid sequence shows 89% identity to that of rat procarboxypeptidase A2, the only A2 form sequenced so far, and 64% identity to that of human procarboxypeptidase A1. The newly determined sequence was modeled to the three-dimensional crystal structures of both bovine carboxypeptidase A and porcine procarboxypeptidase A1 by a novel distance geometry approach. Biases in the modeling were avoided by relying exclusively on automatic procedures and by using random structures as starting points. Information taken from the known homologous structures refers only to the backbone since no explicit data describing the conformation of side chains were transferred. Ten structures of human carboxypeptidase A2 were determined on the basis of each of the two known crystal structures. The root-mean-square distance for the backbone atoms between the 10 structures and their mean for 237 selected residues is 0.7 A when starting from the bovine protein and 0.8 A for 251 selected residues when starting from the porcine protein. The 94 residue-long activation segment was also determined in the modeling based on the porcine zymogen; its structure is well defined but not its orientation with respect to the enzyme moiety. The model obtained for human procarboxypeptidase A2 is discussed with respect to the specificity and activation of the enzyme.

Medullary thyroid carcinoma mimicking an autonomous functioning nodule

A 42-year-old woman with a medullary thyroid carcinoma (MTC) inside of an autonomously functioning thyroid nodule is reported. The patient was initially diagnosed of a hyperfunctioning autonomous thyroid adenoma but the histopathological and immunohistochemistry study were diagnostic for a MTC. This is the first case of a medullary thyroid carcinoma associated with thyroid hyperfunction which was presented as a hot nodule in the scintigraphy. We propose a systematic performance of a fine needle biopsy in all thyroid nodules because of the possibility of carcinoma associated to functioning nodules could be present.

Procarboxypeptidase in rat pancreas. Overall characterization and comparison of the activation processes

Three monomeric procarboxypeptidases and a binary complex consisting of a procarboxypeptidase and a chymotrypsinogen have been isolated from rat pancreas by HPLC. N-terminal sequence determination, substrate-specificity analysis and physico-chemical characterization showed that the carboxypeptidase precursors were the A1, A2 and B forms. No isomorphism could be detected for any of these proenzymes and no clear evidence was obtained for the presence of procarboxypeptidase-containing quaternary complexes of the types previously described for other species. Instead, we observed the presence of a binary complex between procarboxypeptidase A2 and chymotrypsinogen B. Among the major pancreatic endoproteinases, only trypsin was found to be a general activator of rat procarboxypeptidases in vitro. Time-course analysis of the products generated after trypsin addition confirmed that full activation of procarboxypeptidase A1 requires several cleavages in the C-terminal region (residues 87-94) of the activation segment, while procarboxypeptidases A2 and B require a single cleavage each. The carboxypeptidases released participate in the trimming of the activation segment in A1 and B, but not in A2, probably because of the high specificity of the latter in the active form.

Analysis of the contribution of the HLA system to the inheritance in the Wolfram syndrome

The Wolfram syndrome (WS) is an autosomal recessive disorder beginning in childhood that consists of four clinical features: diabetes insipidus, diabetes mellitus, optic atrophy and deafness. Its pathogenesis remains unknown, although the tendency to develop this syndrome has been related to some class II antigens of the HLA system. We report six new cases in four families. A review of published data from the genetic features of this syndrome is performed, establishing the high frequency of the HLA-DR2 antigen in the WS (44.4%) compared with a control group (21.9%; relative risk, 2.8) and to patients with Type 1 insulin-dependent diabetes mellitus (Type 1 diabetes) (6.77%; relative risk, 9.7). We also comment the high frequency of the HLA-DQw1 antigen (85.5%) in this syndrome, without statistical significance. A familial segregation study of the HLA haplotypes has been carried out without finding correlation between the autosomal recessive pattern attributed to the WS, and the major histocompatibility complex. In conclusion, whereas HLA may increase susceptibility to the WS, as shown by the existence of an HLA-DR2 association, the major genetic influence on the inheritance of the WS must be at another locus.

Advances in metallo-procarboxypeptidases. Emerging details on the inhibition mechanism and on the activation process

Our knowledge on the structure and functionality of pancreatic carboxypeptidases is rapidly expanding to include that of their zymogen forms. The recent application of fast and mild isolation procedures, together with modern molecular genetic and biochemical-biophysical characterization approaches, has provided a clearer view of the basic structures and functional states in which these zymogens occur, and their evolutionary relationships. The same holds for related metallo-carboxypeptidases, either in the pro or active forms, that have been isolated and characterized in non-digestive fluids and tissues, where they probably play an important role in protein and peptide processing. The determination of the three-dimensional structure of the A and B pancreatic zymogens has revealed the molecular determinants of their inactivity and proteolytic activation. The folding of their 95-residue activation segment in a globular N-terminal domain (74-81 residues) and in a connecting region (20-14 residues), and the specific contacts of these pieces with the substrate binding sites of the enzyme, are important factors in zymogen inhibition. On the other hand, the different length of the alpha-helical connecting region and the stability of its contacts with the enzyme account for the different activation properties of A and B zymogens.

Pancreatic procarboxypeptidases: their activation processes related to the structural features of the zymogens and activation segments

The molecular events leading to the complete activation of pancreatic procarboxypeptidases A and B have been investigated. For both proteins the activation process follows a similar general scheme: trypsin is responsible for the first cleavage that separates the active enzyme from the activation segment, the degradation of the activation segment proceeds only from its C-terminal end, and activity release can be correlated with the disappearance of the long forms of the activation segment. In both systems, trypsin and the released carboxypeptidase participate in the trimming of the severed activation regions. However, the rate of enzymatic activation is much faster in the case of procarboxypeptidase B. This phenomenon may be explained by some structural differences in the connecting region which acts as a linker between the globular domain of the activation segment and the N-terminal end of carboxypeptidases and also by the higher efficiency of carboxypeptidase B for the digestion of its own activation segment. It is not due to unfolding of the activation domain, since the isolated activation domain retains its globular conformation in solution.

NON-ASSOCIATION BETWEEN 9.2 KB PvuII RFLP AND SERONEGATIVE SPONDYLOARTHROPATHIES IN SPAIN

Several studies of DNA restriction fragment length polymorphism (RFLP) in ankylosing spondylitis (AS) have been carried out. The association between a recently identified class I HLA 9.2 kb PvuII RFLP and AS remain controversial. In order to evaluate this possible association in an Euro-Caucasian population, the genomic DNA of 42 AS patients and 18 patients with Reiter's syndrome (RS) and 42 healthy controls was analysed. Non-association between 9.2 kb PvuII RFLP and AS or RS was observed. As described previously, a strong association between this fragment and HLA-A3 and/or HLA-A9 antigens was demonstrated. A study of two families showed that this RFLP segregates with HLA-A3 and/or HLA-A9 and independently of the HLA-B27. Our findings support the view that the 9.2 kb PvuII fragment is not universally associated with AS.

Differential scanning calorimetric study of carboxypeptidase B, procarboxypeptidase B and its globular activation domain

High-sensitivity differential scanning calorimetry has been applied to the study of porcine pancreatic carboxypeptidase B, the proenzyme and its 81-residue activation domain. The thermal study has been carried out over a range of scan rates, ionic strengths and pH values. The thermal unfolding of the isolated activation domain has been found to be reversible and corresponds to that of a typical compact globular structure, with melting temperatures higher than those of the enzyme and proenzyme. Both proteins, on the other hand, undergo an irreversible, highly scan-rate-dependent thermal denaturation under all the experimental conditions investigated. The denaturation of the enzyme at pH 7.5 and the proenzyme at pH 7.5 and 9.0 follows the two-state irreversible model [Sánchez-Ruiz, J.M., López-Lacomba, J.L., Cortijo, M. & Mateo, P.L. (1988) Biochemistry 27, 1648-1652]. Thus the kinetic constants and activation parameters of the denaturation process could be obtained and compared to those for other proteins, particularly those of the closely related carboxypeptidase A system.

The NMR structure of the activation domain isolated from porcine procarboxypeptidase B

The three-dimensional structure of the activation domain isolated from porcine pancreatic procarboxypeptidase B was determined using 1H NMR spectroscopy. A group of 20 conformers is used to describe the solution structure of this 81 residue polypeptide chain, which has a well-defined backbone fold from residues 11-76 with an average root mean square distance for the backbone atoms of 1.0 +/- 0.1 A relative to the mean of the 20 conformers. The molecular architecture contains a four-stranded beta-sheet with the polypeptide segments 11-17, 36-39, 50-56 and 75-76, two well defined alpha-helices from residues 20-30 and 60-70, and a 3(10) helix from residues 43-46. The three helices are oriented almost exactly antiparallel to each other, are all on the same side of the beta-sheet, and the helix axes from an angle of approximately 45 degrees relative to the direction of the beta-strands. Three segments linking beta-strands and helical secondary structures, with residues 32-35, 39-43 and 56-61, are significantly less well ordered than the rest of the molecule. In the three-dimensional structure two of these loops (residues 32-35 and 56-61) are located close to each other near the protein surface, forming a continuous region of increased mobility, and the third disordered loop is separated from this region only by the peripheral beta-strand 36-39 and precedes the short 3(10) helix.

Autolysis of proproteinase E in bovine procarboxypeptidase A ternary complex gives rise to subunit III

Extracts of bovine pancreatic tissue are shown by HPLC to contain two distinct ternary complexes of procarboxypeptidase A (subunit I), chymotrypsinogen C (subunit II) and either proproteinase E or subunit III. It is shown that proproteinase E in the complex generates subunit III by removal of 13 N-terminal residues when the former is allowed to autolyze in solution or when catalytic amounts of isolated active proteinase E are added to it. Autolysis of proproteinase E was accompanied by the loss of potential activity towards specific synthetic substrates and occurred at a higher rate in pancreatic juice than in pancreatic tissue extracts, even when both were processed in the presence of serine protease inhibitors. We conclude that subunit III (also called truncated protease E) is an autolytic product of proproteinase E and not an ab initio component of the native ternary complex.

Sequence-specific 1H NMR assignments and determination of the secondary structure for the activation domain isolated from pancreatic procarboxypeptidase B

Nearly complete sequence-specific 1H NMR assignments are presented for amino acid residues 3-81 in the 81-residue globular activation domain of porcine pancreatic procarboxypeptidase B isolated after limited tryptic proteolysis of the zymogen. These resonance assignments are consistent with the chemically determined amino acid sequence. Regular secondary structure elements were identified from nuclear Overhauser effects and the sequence locations of slowly exchanging backbone amide protons. The molecule contains two alpha-helices, including residues 20-30 and approximately residues 58-72, and a three-stranded antiparallel beta-sheet with the individual strands extending approximately from 12 to 17, 50 to 55, and 75 to 77. The identification of these secondary structures and a preliminary analysis of additional long-range NOE distance constraints show that isolated activation domain B forms a stable structure with the typical traits of a globular protein. The data presented here are the basis for the determination of the complete three-dimensional structure of activation domain B, which is currently in progress.

Human insulin dosage and distribution at the onset of type 1 diabetes mellitus

The total insulin dosage and its distribution throughout the day were evaluated in newly diagnosed Spanish IDDM patients treated with semisynthetic human insulin. We assessed the insulin dosage and its distribution modifications related to an inpatient versus outpatient setting. We compared our results with classical theoretical algorithms based on patients treated with animal insulin and with alimentary habits which differ from our geographical area. The initial total daily dose (0.68 +/- 0.27 U/kg per day) did not substantially differ from the usual recommended dose (0.70-0.80 U/kg per day). A substantial decrease in total insulin dose was observed in ambulatory patients (0.55 U/kg per day). The reduction in dosage when we substituted regular insulin for intermediate acting insulin was smaller than what is commonly advised. A very low proportion of patients needed to add extra regular insulin to the pre-dinner intermediate insulin dose to achieve acceptable glucose control. Moreover, in these cases regular insulin comprised only 10% of total daily dosage, a proportion clearly inferior to that recommended. The majority of this group of patients needing regular insulin plus intermediate insulin at pre-dinner were treated with human zinc insulin. Most of our patients were acceptably controlled with a regular insulin dose before breakfast and lunch and an intermediate dose before dinner. Finally, human insulin pharmacokinetics plus our Mediterranean alimentary habits might be the explanation to our findings.

The tryptic activation pathway of monomeric procarboxypeptidase A

Procarboxypeptidases are the remaining major digestive zymogens the activation process of which remains unsolved. Here it is shown that in the tryptic activation of monomeric procarboxypeptidase A from porcine pancreas, the generation of carboxypeptidase A (CPA) activity parallels the limited proteolysis of the 94-residue activation segment. This degradation proceeds from the COOH-terminal end of the molecule, and CPA itself makes an important and unexpected contribution by excising the COOH-terminal arginine residue of the released primary activation fragment. Successive cleavages at some of the peptide bonds of the activation segment nearest to the COOH terminus were found to be of prime importance in eliciting CPA activity, particularly those involving the carbonyl groups of Arg94 and Gly93 which were first cleaved. It is also shown that the rate of activation does not depend directly upon the generation of CPA-alpha and its conversion to CPA-beta.

1H-n.m.r. studies of the isolated activation segment from pig procarboxypeptidase A

The isolated activation segment (asA) from pig pancreatic procarboxypeptidase A was studied by 1H-n.m.r. spectroscopy over a wide range of solution conditions. Isolated asA shows many characteristics of compactly folded globular proteins, such as the observation of perturbed positions for resonances from methyl groups, alpha-carbon atoms, histidine residues and the tyrosine residue. The single tyrosine residue (Tyr-70) exhibits a very high pKa, and both histidine and tyrosine residues show slow chemical modification (deuteration and iodination). In contrast, asA shows rapid NH exchange. Analysis of the spectra by pH titration and nuclear Overhauser effects revealed several residue interactions. Quantitative analysis of deuterium and tritium exchange allowed the assignment of the histidine C-2-H resonances to their respective residues in the sequence. His-66, the closest to the sites of proteolytic attack in the proenzyme, is shown to be the most accessible to solvent in procarboxypeptidase A. It was also shown that asA is thermally very stable ['melting' temperature (Tm) 88 degrees C] and requires a high urea concentration for denaturation (6.25 M, at pH 7.5). Evidence is presented for some degree of conformational flexibility in the premelting range, a feature that could be ascribed to the preponderance of helical secondary structure and to the lack of disulphide bridges. The free solution structure of asA is probably unchanged when it binds to carboxypeptidase A.

Primary intrapulmonary benign schwannoma. A case with ultrastructural and immunohistochemical confirmation

Neurogenic pulmonary tumours are rare. Neurofibromas are the most common variety and tend to occur in patients with generalized neurofibromatosis, whereas schwannomas arise sporadically in patients who have no evidence of this disorder. A case of solitary benign schwannoma arising in a segmental bronchus is presented, and the published cases reviewed. Microscopically, the tumour had a spindle-shaped cell proliferation with palisade formation in several fields and low cellularity in other areas. The diagnosis was supported by positive immunostaining for S-100 protein and by ultrastructural examination which showed elongated cells surrounded by well-preserved basal lamina and numerous cytoplasmic processes also possessing a basal lamina.

Primary intrapulmonary benign schwannoma. A case with ultrastructural and immunohistochemical confirmation

Neurogenic pulmonary tumours are rare. Neurofibromas are the most common variety and tend to occur in patients with generalized neurofibromatosis, whereas schwannomas arise sporadically in patients who have no evidence of this disorder. A case of solitary benign schwannoma arising in a segmental bronchus is presented, and the published cases reviewed. Microscopically, the tumour had a spindle-shaped cell proliferation with palisade formation in several fields and low cellularity in other areas. The diagnosis was supported by positive immunostaining for S-100 protein and by ultrastructural examination which showed elongated cells surrounded by well-preserved basal lamina and numerous cytoplasmic processes also possessing a basal lamina.

Procarboxypeptidase A activation segment compared to structures of other proteins

The 94-residue activation segment of procarboxypeptidase A was compared with segments of other proteins. No significant homologies were observed towards other activation segments, but an inter-domain segment preceding the serine-protease part of complement factor B showed some structural relationships with the N-terminal region of the procarboxypeptidase A activation segment. This may reflect common functional and organizational patterns. In contrast, the present comparisons do not give functional or further sequence support to previously proposed structural homologies with helix-loop-helix (EF-hand) calcium-binding proteins.

[Evaluation of the treatment of Cushing's syndrome using ketoconazole]

The effectiveness of ketoconazole for the therapy of Cushing's syndrome, both of adrenal and pituitary origin, was retrospectively evaluated. To this end, the clinical and hormonal results in 5 patients were assessed. There were 4 females and one male, with ages ranging between 17 and 64 years. Three of them, who had Cushing's disease, received sustained treatment with ketoconazole when other therapeutic measures had failed. The two remaining patients (one with Cushing's disease and the other with adrenal adenoma) were treated with this drug in the preoperative period to alleviate the deterioration in the clinical condition caused by hypercortisolism. The clinical evolution of the patients is described, as well as the plasma adrenocorticotropin (ACTH) and the free cortisol in 24 hour urine in the subsequent controls. In view of the study results, we feel that ketoconazole is an effective treatment for the long term control of Cushing's syndrome. In addition, it may be also useful as preoperative therapy in those patients severely deteriorated by the sustained hypercortisolism.

The separation of pancreatic procarboxypeptidases by high-performance liquid chromatography and chromatofocusing

Different experimental conditions and chromatographic supports have been selected for the most efficient and rapid purification of procarboxypeptidases from porcine and human pancreas by different high-performance liquid chromatography (HPLC) variants (anion exchange, reversed phase and gel filtration). Anion-exchange chromatography was found to be the most capable and permitted the isolation, in a single step, of three different porcine procarboxypeptidases (2A + 1B forms) and five different human procarboxypeptidases (2B + 3A forms) in a native and pure state from whole pancreas extracts. Other pancreatic proproteases are also cleanly isolated in the same step. Reversed-phase chromatography under mild conditions separated porcine or human procarboxypeptidases A from other pancreatic proteins in a very short time but was unable further to subfractionate the same proteins. The sequential use of gel filtration (or anion-exchange) and reversed-phase HPLC chromatography permitted, in a simple way, the isolation and dissociation of the strongly bound components of the binary complexes between procarboxypeptidases A and proproteinase E in either porcine or human pancreas extracts. Chromatofocusing on a fast protein liquid chromatographic support was also found to be a very efficient technique, showing a slightly lower capability to separate procarboxypeptidases than anion-exchange HPLC though in a much shorter time and in larger quantities.

Late-onset hypocalcemia appearing years after thyroid surgery

We revised four cases of hypocalcemia diagnosed yr after thyroid surgery, including 1 man and 3 women, operated 5-23 yr before the onset of symptoms, which ranged from mild paresthesia to convulsive seizures. Total serum calcium levels ranged from 1.1 to 2.05 mmol/l, and PTH levels were low in the 3 cases in which they were measured. Hypoparathyroidism appearing as late-onset hypocalcemia after extense thyroid surgery is a poorly understood condition, perhaps not as unfrequent as it is considered.

[Cushing's disease in a patient with primary empty sella turcica]

Primary empty sella is a neuroanatomical condition which is more common in middle aged obese multiparous females with long-standing hypertension. Usually there are no symptoms, but occasionally nonspecific headache may be present. Hormone studies are commonly normal in these patients, although several functional hypothalamic and pituitary abnormalities have been reported. We report a 64-year-old female with primary empty sella in whom Cushing's disease was diagnosed. The association of both disorders is exceptional.

A case with persistent nephrogenic diabetes insipidus following parathyroidectomy for hyperparathyroidism

A 25-year-old woman with persistent nephrogenic diabetes insipidus (NDI) following parathyroidectomy for primary hyperparathyroidism is described. NDI is a well recognized complication of primary hyperparathyroidism, generally imputed to hypercalcemia, and promptly reversible after correcting it. In our case, the impaired concentrating ability of the renal tubule was irreversible after the removal of the parathyroid adenoma and the correction of the hypercalcemia, presumptively due to the morphological irreversible changes in the kidney. In addition, hypercalciuria persisted and was the cause of a compensatory hyperparathyroidism. Treatment with thiazide diuretic was effective to decrease relative hypercalciuria, thus reversing the compensatory hyperparathyroidism.

Analysis of the conformation and ligand-binding properties of the activation segment of pig procarboxypeptidase A

The isolated activation segment of pig procarboxypeptidase A binds two Tb3+ ions in a strong and specific way. In contrast, the binding of Ca2+, Cd2+ and Mg2+ is weak. The binding of Tb3+ increases the resistance of the isolated activation segment against proteolysis and competes for the binding of the carbocyanine dye Stains-All. This dye forms complexes with the activation segment showing spectral properties similar to those observed with EF-hand structures. The presented results support a previous hypothesis on the existence of two regions in the activation segment of pancreatic procarboxypeptidases structurally related to Ca2+-binding domains of the EF-hand protein family.

Erythromelalgia associated with acute diabetic neuropathy: an unusual condition

Erythromelalgia is a syndrome characterized by erythema, burning pain and increased skin temperature of the affected extremities. It can be either primary (idiopathic) or secondary, but both forms require a critical temperature between 32-36 degrees C to provoke the crisis. Among the secondary forms, its association with diabetes mellitus is infrequent and its significance is little known. The histological studies have been fundamentally performed in patients with this syndrome affected by thrombocythemia; vascular thrombosis and fibromuscular intimal arteriolar proliferation were the prominent findings not corroborated in patients with the primary form. We studied one patient with acute diabetic neuropathy who developed erythromelalgia. We noted the absence of histopathological lesions, suggesting a disorder in vascular motility regulation favored by the severe neuropathy, without being able to discount a possible immunomediated mechanism. We describe the favourable evolution of the patient after treatment with aspirin and methysergide.

Conformational predictive studies on the activation segment of pancreatic procarboxypeptidases

Little is known about the conformation and evolutionary origin of the activation segment of pancreatic procarboxypeptidases. Analysis of the sequence and secondary structure propensities of these propeptide segments indicate that they contain two regions structurally related to the Ca2+-binding sites of the EF-hand protein family. This proposed homology could explain how (and why) carboxypeptidases developed such long (94 residues) activation peptides.

Primary structure of the activation segment of procarboxypeptidase A from porcine pancreas

The complete primary structure of the activation segment of monomeric procarboxypeptidase A from porcine pancreas has been determined by automated and manual Edman-like degradation methods performed on its fragments generated by enzymatic cleavage. The polypeptide consists of 94 residues, with a molecular mass of 10,768, and presents a high proportion of acidic and hydrophobic residues and a proline-rich region in the center of the molecule. Comparison of this sequence with the already reported equivalent sequence deduced from rat procarboxypeptidase A cDNA reveals a very high degree of homology between the two propeptides (up to a 81% of identities), which is even higher in certain large zones of the molecule.

Preparative isolation of the two forms of pig pancreatic pro-(carboxypeptidase A) and their monomeric carboxypeptidases A

A method is reported for the preparative isolation of the two forms of pro-(carboxypeptidase A) from pig pancreas: the monomer and the binary complex with pro-(proteinase E). This method, which is mainly based on chromatography on DEAE-Sepharose at pH 5.7, allows these proenzymes to be prepared more quickly and in safer conditions than with other reported methods. Undegraded and homogeneous carboxypeptidase A1 and A2 species (peptidyl-L-amino acid hydrolase, EC 3.4.17.1), in monomeric forms with high specific activity, are also obtained in high yield by controlled trypsin activation of either of the pro-(carboxypeptidases A) followed by chromatography on DEAE-Sepharose at pH 5.8 under dissociating conditions (7 M-urea).