Characterization of a new cysteine proteinase inhibitor of human saliva, cystatin SN, which is immunologically related to cystatin S

A new cysteine proteinase inhibitor, cystatin SN, was purified from human whole saliva by chromatography with DE32, Sephacryl S200, and CM-Sepharose CL6B. Cystatin SN is immunologically related to cystatin S and both inhibitors have a similar molecular mass of about 13 kDa. The new inhibitor, however, was clearly distinguished from cystatin S by its much higher pI value. These inhibitors showed similar inhibitory activity for ficin, but cystatin SN was a much better inhibitor for papain and dipeptidyl peptidase I. The amino acid sequence of cystatin SN deduced in the light of the known structure of cystatin S indicates that they have 10 different amino acid residues in the sequence comprising in total 113 residues.

Inhibition of calcium-carbonate precipitation by human salivary proline-rich phosphoproteins

The effects of the proline-rich phosphoproteins (PRP) on the rate of precipitation of CaCO3 from a CaCO3-supersaturated solution were examined by recording the absorbance at 570 nm and the pH, when 20 mM CaCl2 was added to 20 mM NaHCO3, in the presence or absence of proteins. The PRP suppressed CaCO3 nucleation and exhibited inhibitory effects on CaCO3 precipitation under those conditions and under stimulated physiological conditions (final concentration of Ca2+ was 2 mM and that of HCO-3 60 mM, pH was 8.0 at 37 degrees C). PRP may be of biological significance in maintaining homeostasis of the buffering system of saliva, which is mainly composed of bicarbonate, and in preventing the formation of stones consisting of CaCO3 in the salivary ducts.

Intracellular localization of salivary peptide P-C-like immunoreactivity in the human pancreatic B-cells

In order to clarify the intracellular localization of salivary peptide P-C-like immunoreactivity in human pancreatic B-cells, an immunohistochemical study at electron microscopic levels was carried out by the protein A-gold technique using antisera against insulin and salivary peptide P-C. Both salivary peptide P-C-like immunoreactivity and insulin-like immunoreactivity were present only in the insulin secretory granules of the pancreatic B-cells. However, the former immunoreactivity was lacking in many insulin secretory granules of foetal pancreatic B-cells while the latter immunoreactivity was seen in all insulin secretory granules. Salivary peptide P-C-like immunoreactivity was not found in the other kinds of cells in the islets. In a previous immunohistochemical study at light microscopic level, salivary peptide P-C-like immunoreactivity appeared in a few pancreatic B-cells at about the 16th week of gestation, in an increasing number during gestation, and was seen in all pancreatic B-cells a few months after birth. The present finding together with the above results suggest that absence of salivary peptide P-C-like immunoreactivity in some foetal pancreatic B-cells may be due to the underdevelopment of salivary peptide P-C-like immunoreactivity in each insulin secretory granule. From the examination of cross-reactivity of antisera against salivary peptide P-C to other kinds of salivary peptides and salivary Protein C, and from the results of an indirect immunofluorescence technique using three kinds of antisera including antisera against salivary peptide P-C, salivary peptide P-B and salivary Protein C, it was thought that salivary peptide P-C-like immunoreactivity in human pancreatic B-cells belongs neither to salivary Protein C nor to salivary peptide P-B nor to salivary peptide P-E, but either to salivary peptide P-C itself or to an unknown substance which has common antigenic determinants with salivary peptide P-C, salivary peptide P-B and salivary Protein C. Salivary peptide P-C-like immunoreactivity was not found in the pancreatic B-cells of other mammals. Thus, although a new substance other than insulin is present in the insulin secretory granules of the human pancreatic B-cells, its pathophysiological function remains unclear.

Presence of salivary protein C and salivary peptide P-C-like immunoreactivity in the laryngo-tracheo-bronchial glands

An indirect immunofluorescence technique using antisera against salivary peptide P-C and against salivary Protein C was carried out on the laryngeal, tracheal and bronchial glands to examine whether salivary peptide P-C-like immunoreactivity, recently demonstrated in the serous cells of the human salivary glands, was also present in those of laryngeal, tracheal and bronchial glands and to ascertain whether salivary peptide P-C is a fragment of salivary Protein C or not. Salivary peptide P-C-like immunoreactivity was present in the serous cells of the human laryngeal, tracheal and bronchial glands. Observation of serial sections immunostained with two kinds of antisera revealed that cells reacting with antisera against salivary peptide P-C were identical to those reacting with antisera against salivary Protein C pre-incubated with salivary peptide P-C. The finding implied that salivary peptide P-C and salivary Protein C, originally isolated from human saliva, were also present in the serous cells of tissues other than the salivary glands. Furthermore, analysis of the primary structure of salivary peptide P-C and salivary Protein C together with the present morphological finding suggests that salivary peptide P-C is a COOH-terminal fragment of salivary Protein C. Thus, salivary Protein C and salivary peptide P-C may play some role in the function of the serous cells of the salivary and laryngo-tracheo-bronchial glands.

Cystatin S: a cysteine proteinase inhibitor of human saliva

An acidic protein of human saliva, which we named SAP-1 previously, is now shown to be an inhibitor of several cysteine proteinases. The protein inhibited papain and ficin strongly, and stem bromelain and bovine cathepsin C partially. However, it did not inhibit either porcine cathepsin B or clostripain. The mode of the inhibition of papain was found to be non-competitive. The name cystatin S has been proposed for this salivary protein in view of the similarities in activity and structure to other cysteine proteinase inhibitors such as chicken egg-white cystatin and human cystatins A, B, and C. The cystatin S antigen was detected immunohistochemically in the serous cells of human parotid and submaxillary glands.

[A study on salivary peptide P-C with special reference to intracellular localization of salivary peptide P-C like immunoreactivity in the human pancreatic B-cells]

In order to clarify the intracellular localization of salivary peptide P-C like immunoreactivity in the human pancreatic B-cells, an immuno-electronmicroscopical study using protein A-gold technique was carried out on the human foetal pancreas. Salivary peptide P-C like immunoreactivity was present in some of insulin secretory granules while insulin like immunoreactivity was found in all insulin secretory granules. The finding suggested that new substance in addition to insulin and its precursor was present in the insulin secretory granules of the human pancreatic B-cells. Furthermore, the finding seemed to explain the previous study that development of salivary peptide'P-C like immunoreactivity in the foetal pancreatic B-cells was immature in compared to that in the human adult pancreatic B-cells. In addition, to examine whether or not, salivary peptide P-C like immunoreactivity in the human pancreatic B-cells is Salivary Protein C, an indirect immunofluorescence technique using three kinds of antisera against salivary peptide P-C, Salivary Protein C and salivary peptide P-B, and using their antigens was undertaken on the adult pancrease. From the results of the study, it was thought that salivary peptide P-C like immunoreactivity in the human pancreas was neither Salivary Protein C itself, nor salivary peptide P-B itself, but was either salivary peptide P-C itself or unknown substance which had the common antigenic determinant with salivary peptide P-C, P-B and Salivary Protein C, since salivary peptide P-C like immunoreactivity in the human pancreas disappeared in the sections in which P-C antisera preincubated with each of salivary peptide P-C, P-B and Salivary Protein C were used as the primary antisera. Thus, although new substance was present in the insulin secretory granules of the human pancreatic B-cells, its pathophysiological role remained to be elucidated.

Primary structure of cat osteocalcin

A bone Gla-containing protein (osteocalcin) of cat has been isolated and the complete primary structure has been determined to be YLAPGLGAOAPYPDPLXPKRXICXLNPDCDELADHIGFQDAYRRFYGTV. The protein consists of 49 amino acid residues (Mr. 5,641) containing three Gla residues and a single disulfide bond. Although the C-terminal 30 residues (20th to 49th) of the sequences of cow, monkey, and human osteocalcins are identical, three amino acid substitutions occur at positions 22, 40, and 48 in the case of cat. These substitutions can be explained by single point mutations.

Isolation and amino acid sequence of SAP-1, an acidic protein of human whole saliva, and sequence homology with human gamma-trace

A low-molecular-weight acidic protein was isolated from human whole saliva by DE32 column chromatography and designated as SAP-1. The amino acid sequence was determined by conventional methods to be (sequence in text). The protein consisted of 113 residues and the calculated molecular weight was 12,552. Computer analysis revealed the presence of 54% sequence homology between SAP-1 and gamma-trace, a basic microprotein present in cerebrospinal fluid and in urine of patients with renal failure.

Conformational study of the basic proline-rich polypeptides from human parotid saliva

The conformational study of two basic proline-rich polypeptides from human parotid saliva, P--D and P--E of known primary structures, was performed by CD and 1H--n.m.r. spectra measurements. These polypeptides contain consecutive sequences of five prolyl residues in their amino acid sequences. The troughs in CD spectra of P--D and P--E were found at 202 and 201 nm, respectively. These wavelengths were different from the value of 206 nm of poly-L-proline form II conformation. In spite of this, the existence of poly-L-proline form II conformation was suggested in the structure of P--D, because the trough for a fragmental peptide of P--D containing five consecutive prolyl residues was found at 204 nm. No remarkable change was detected in CD and 1H--n.m.r. spectra of P--D and P--E in the range of pH 3.0-11.0. The result suggests that no folding of polypeptide which might be affected by ionic interaction exists in its structure.

[A study on salivary proline-rich peptide P-C with special reference to the presence of salivary peptide P-C in the human respiratory tract]

In order to elucidate whether Salivary Protein C and salivary peptide P-C, originally isolated from human saliva were present in tissues other than those of the salivary glands or not, an indirect immunofluorescence technique using both antisera against salivary peptide P-C and Salivary Protein C was carried out on human salivary glands and the human respiratory tract. As salivary peptide P-C-like immunoreactivity was detected in the serous cells of salivary glands by previous immunohistochemical study, the human respiratory tract was closed as model tissue, since tracheal and bronchial glands in the human respiratory tract consist of mucous and serous cells. Furthermore, to check whether salivary peptide P-C is a fragment of Salivary Protein C or not, the same immunohistochemical study was undertaken on the serial sections of salivary glands and the respiratory tract. Salivary peptide P-C and Salivary Protein C-like immunoreactivities were present in the serous cells of human salivary glands and in tracheal and bronchial cells. Furthermore, the same serous cells were immunostained with antisera against salivary peptide P-C, with antisera against Salivary Protein C and with antisera against Salivary Protein C preabsorbed with salivary peptide P-C. In view of the fact that the full sequence of salivary peptide P-C is identical to the COOH terminal 44 amino acid residues of Salivary Protein C, it was suggested that the full sequence of Salivary Protein C was present in the serous cells of human salivary glands and in those of tracheal and bronchial glands and that salivary peptide P-C was a fragment of Salivary Protein C.(ABSTRACT TRUNCATED AT 250 WORDS)

Further fractionation of basic proline-rich peptides from human parotid saliva and complete amino acid sequence of basic proline-rich peptide P-H

Three basic proline-rich peptides were newly isolated from human parotid saliva, and designated as P-G, P-H, and P-I. The amino acid sequence of P-H was determined to be Ser-Pro-Pro-Gly-Lys-Pro-Gln-Gly-Pro-Pro-Gln-Gln-Glu-Gly-Asn-Asn- Pro-Gln-Gly-Pro-Pro-Pro-Pro-Ala-Gly-Gly-Asn-Pro-Gln-Gln-Pro-Gln-Ala-Pro-Pro- Ala-Gly-Gln-Pro-Gln-Gly-Pro-Pro-Arg-Pro-Pro-Gln-Gly-Gly-Arg-Pro-Ser-Arg-Pro- Pro-Gln by conventional methods. The amino terminal ten residues of P-H were the same as those of proline-rich peptides P-D, P-E, and P-F reported previously. Comparison of the amino acid sequences between P-H and P-D revealed that there are two deletion parts and several amino acid substitutions in the sequence of P-H. Homology between P-H and P-D was as high as 70%.

[Salivary peptide P-C (III). Its relation to the pathogenesis of diabetes mellitus]

Previous immunohistochemical study showed that salivary peptide P-C like immunoreactivity, originally isolated from whole human saliva, was present not only in human salivary glands but also in human pancreatic B-cells. To elucidate the pathophysiological role of this peptide-like immunoreactivity in human pancreatic B-cells, immunohistochemical study using antisera against both insulin and peptide P-C was carried out on the paraffin embedded pancreatic tissues of 27 diabetic patients and 30 control subjects. Positive immunofluorescence due to insulin was detected in 96% of the diabetic pancreases and 100% of the controls. A pancreas of only one IDDM did not have any immunofluorescence due to insulin. Thus, no significant differences were seen in connection with the presence of insulin between pancreases of NIDDM and the controls, though the present study did not examine whether the number of pancreatic B-cells in the pancreas of NIDDM was the same as that in the controls or not. In contrast, positive immunofluorescence due to peptide P-C like immunoreactivity was demonstrated in only 41% of the diabetic pancreases but in 87% of the controls. In view of the fact that the diabetic pancreases and the controls were fixed and embedded into paraffin in the same department of pathology and under the same conditions, the negative finding for salivary peptide P-C like immunoreactive in the diabetic pancreas seems to result neither from the effects of fixatives nor the destructive postmortem effects of enzymes on the antigenicity of peptide P-C like immunoreactivity but from the decreased content of peptide P-C like immunoreactivity in the diabetic pancreas.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of salivary peptide P-C like immunoreactivity in human pancreatic B-cells

Abstract. An immunohistochemical study using antisera against proline rich salivary peptide P-C and insulin, glucagon, somatostatin and pancreatic polypeptide antisera was carried out on the foetal pancreas at different stages and on the newborn infant's, infant's, child's and adult pancreas to examine the time at which salivary peptide P-C like immunoreactivity appeared in the human pancreas. Salivary peptide P-C like immunoreactive cells first appeared as a few scattered cells in the foetal pancreas after 16 weeks of gestation and gradually increased in numbers during gestation. The cells corresponded only to insulin immunoreactive cells in the foetal, newborn infant's, infant's, child's and adult pancreas. Only some of the insulin immunoreactive cells in the foetal pancreas contained salivary peptide P-C like immunoreactivity while the majority of those in the infant's pancreas and all those in the child's and adult pancreas did so. The findings, together with the fact that the full sequence of salivary peptide P-C is identical to the COOH-terminal 44 amino acid residues of Salivary Protein C, led to the possibility that peptide P-C like immunoreactivity in the human pancreatic B-cells was not a moiety of the precursor of insulin and pro-insulin, but a moiety of Salivary Protein C. It has been suggested that, in saliva, Salivary Protein C aids in maintenance of the calcium concentration. Based on the hypothesis that peptide P-C like immunoreactivity in the human pancreatic B-cells may play some role in insulin release through the maintenance of the calcium concentration, the present finding seems to explain the fact that the mechanism for insulin release in the foetal pancreas is immature in spite of sufficient biosynthesis of insulin.

Immunohistochemical demonstration of salivary proline rich peptide P-C like immunoreactivity in human pancreatic B-cells

Antisera against proline rich peptide P-C, recently isolated from human whole saliva were raised in rabbits by injections of peptide P-C-BSA conjugates. Immunohistochemical study using the antisera was carried out on human salivary glands, gut and pancreas. The results showed that peptide P-C like immunoreactivity was present not only in the salivary glands but also in the pancreatic islets, though not in the gut. Furthermore, immunostaining of adjacent thin sections revealed that cells reacting with antisera against peptide P-C were identical to those reacting with insulin antisera. As the antisera against peptide P-C did not have any cross-reactivities to insulin, glucagon, somatostatin, pancreatic polypeptide, VIP and human C-peptide, the antisera were considered to recognize specifically either peptide P-C related antigen or peptide P-C itself in human pancreatic B-cells. A novel substance, peptide P-C like immunoreactivity, may be present in pancreatic B-cells independent of pro-insulin and insulin. Morphological similarity between the salivary glands and the pancreas has been reported, and amylase, kallikrein and glucagon are present in both. These findings seem to suggest some functional relation between the pancreas and salivary glands. Detection of peptide P-C like immunoreactivity in the pancreas and salivary glands would be a additional support for this idea. Although it is suggested that peptide P-C like immunoreactivity in pancreatic B-cells may play some role in the function of B-cells, its exact pathophysiological role remains obscure.