PubMed Health⌕ Search

Biomedical subjects

C Lazure

Publications and source records attributed to C Lazure.

At least 127 records · Page 7Linked to original sources
PubMed1985

On the circulating form of atrial natriuretic factor.

Isolation and sequencing of IR-ANF from plasma reveal that the circulating form of ANF is a 28-amino acid peptide (Ser 99-Tyr 126) which inhibits basal aldosterone secretion from suspensions of rat zona glomerulosa cells to the same extent as synthetic Arg 101-Tyr 126. The same form (minus two N-terminal amino acids) (Arg 101-Tyr 126) has been isolated from culture media of atrial cardiocytes and sequenced. Structure activity studies of shorter, N- or C-terminally truncated versions of synthetic Arg 101-Tyr 126 show that the latter is the most potent one.

Amino Acid Sequence↗
PubMed1984

Structure-activity relationships of atrial natriuretic factor (ANF). I. Natriuretic activity and relaxation of intestinal smooth muscle.

Atrial natriuretic factor-related peptides were produced from synthetic ANF (101-126) either by chemical hydrolysis at the N-terminal end or by treatment with carboxypeptidases at the C-terminal end. The biological activities of these peptides were characterized in vivo by a natriuretic bioassay and in vitro by relaxation of contracted intestinal smooth muscle (chick rectum). In the natriuretic assay, the removal of Asn122, Ser123 and Phe124 at the C-terminal end alters considerably the renal response. Deletion or extension of amino acids at the N-terminal end affects only slightly the natriuretic activity. Removal of N-terminal or C-terminal amino acids decreases the relaxant activity of ANF on the chick rectum. In both bioassays, simultaneous deletions of residues at both ends drastically affect the activity in an additive manner.

Amino Acid Sequence↗
PubMed1984

The major androgen-dependent protease in dog prostate belongs to the kallikrein family: confirmation by partial amino acid sequencing.

Canine prostate fluids and seminal plasma contain a major androgen-dependent protein which was identified as a proteolytic enzyme exhibiting an Arg-esterase activity. This protease, as characterized, is shown to be present as a two-chain structure held together by at least one disulfide bridge and composed of approximately 220 amino acids. Amino acid sequence determination of both chains has revealed a clear homology to other known amino acid sequences of serine proteases. Furthermore, the comparison of the presented 58 amino acids of the Arg-esterase with the other sequences revealed a very strong homology (larger than 50%) to members of the kallikrein family. The two chain structure could thus result from autolysis of a single chain enzyme in the 'kallikrein autolysis loop'. Amino acid composition of the canine prostatic enzyme suggests that it is related, but not identical, to pancreatic canine kallikrein.

Amino Acid Sequence↗
PubMed1984

Atrial pronatriodilatin: a precursor for natriuretic factor and cardiodilatin. Amino acid sequence evidence.

Numerous peptides isolated from rat heart atria, including two containing 33 and 73 amino acids, were isolated and shown to exhibit natriuretic activities. Here, we describe the purification and partial amino acid sequence of a 106-residue peptide containing the previously sequenced 33- and 73-amino-acid ANF peptides. The determined sequence is a novel one and is not significantly homologous to any known protein or segment thereof. In fact, this sequence shows significant homology only to another novel partial sequence obtained from sequence analysis of a porcine peptide, called cardiodilatin, also found in heart atria. This relationship is taken as evidence that ANF and cardiodilatin are part of the same precursor molecule which would contain at the very least 126 amino acids.

Amino Acid Sequence↗
PubMed1984

Primary structure of a high Mr form of rat atrial natriuretic factor.

During the purification of rat atrial natriuretic factor (ANF), low, intermediate and high Mr forms were observed. In this report we describe the purification and amino acid sequence of a 73 residue peptide containing at its C-terminus the previously sequenced 33 amino acid ANF peptide. The cleavage necessary to produce the 33 amino acid ANF from the 73 amino acid precursor occurs at a Leu-Leu bond. We also report the amino acid composition of an even longer form of ANF containing about 103 residues, in which the extension is amino terminal to the 73 peptide. A computer data bank search showed that the determined sequence is a novel one and is not homologous to any known proteins or segment thereof. The natriuretic activity of the 73 amino acid form when compared to that of a synthetic ANF peptide, comprising the sequence of the last 26 amino acids of ANF, was found to be slightly lower.

Amino Acid Sequence↗
PubMed1984

Amino acid sequence of homologous rat atrial peptides: natriuretic activity of native and synthetic forms.

A substance called atrial natriuretic factor (ANF), localized in secretory granules of atrial cardiocytes, was isolated as four homologous natriuretic peptides from homogenates of rat atria. The complete sequence of the longest form showed that it is composed of 33 amino acids. The three other shorter forms (2-33, 3-33, and 8-33) represent amino-terminally truncated versions of the 33 amino acid parent molecule as shown by analysis of sequence, amino acid composition, or both. The proposed primary structure agrees entirely with the amino acid composition and reveals no significant sequence homology with any known protein or segment of protein. The short form ANF-(8-33) was synthesized by a multi-fragment condensation approach and the synthetic product was shown to exhibit specific activity comparable to that of the natural ANF-(3-33).

Amino Acid Sequence↗
PubMed1984

Comparison of four different carboxylterminal tracers in a radioimmunoassay specific to the 68-84 region of human parathyroid hormone.

Two synthetic carboxylterminal fragments, [tyr52]hPTH(52-84) and [tyr63]hPTH(63-84), and purified bPTH(1-84) were iodinated with 125Iodine to be compared as tracers in a late carboxylterminal radioimmunoassay. Tracer 125I-bPTH(41-84) was generated in vitro by incubating 125I-bPTH(1-84) with plasma membranes of rat kidney cortex. Region specificity was achieved by saturating the unwanted middle component of our multivalent antiserum with a molar excess of hPTH(44-68). A charcoal-dextran separation was worked out for each tracer. The titer of the antiserum giving approximately equal to 30% specific binding of each tracer was used in all experiments. Displacement of each tracer with increasing molar concentration of hPTH(1-84), hPTH(53-84), hPTH(41-84) and of hPTH (64-84) was studied. hPTH(41-84) was also generated by incubating hPTH(1-84) with rat cortex kidney membranes and was calibrated against a commercial preparation of bPTH(37-84). A progressive increase in the titer of the antiserum was seen as the molecular weight of the tracers decreased from a titer of 1/20,000 with 125I-bPTH(1-84) to a titer of 1/50,000 with the two synthetic tracers. Similarly the so-called damage seen during the charcoal-dextran separation in absence of antibody was reduced from 16.0 +/- 6.2% (mean +/- SD) with 125I-bPTH(1-84) to 1.3 +/- .2 with the two synthetic tracers. 50% displacement of the 125I-bPTH(1-84) tracer was achieved at 13.2 +/- .8 fmol/tube for hPTH(1-84) and at 6.3 +/- 1.0 fmol/tube for hPTH(41-84), reflecting the greater reactivity of fragments in that system. With the two synthetic tracers, a concentration of 5.0 +/- .4 fmol/tube of hPTH(1-84) or of 3.5 +/- 1.2 fmol/tube of hPTH(41-84) was necessary to achieve the same goal. With 125I-bPTH(41-84) results were between the two extremes. These results indicated that an increase in antiserum titer, a decrease in assay damage, an improvement in assay sensitivity and in comparative molar reactivity of the various circulating forms of hPTH can be achieved by using synthetic carboxylterminal fragments as tracers in region specific radioimmunoassays of hPTH.

Animals↗
PubMed1984

Subcellular fractionation of pituitary neurointermediate lobes: revelation of various basic proteases.

Homogenates of rat neurointermediate lobes were purified by centrifugation on a Percoll gradient. Lysates of the Percoll gradient fractions were incubated with a synthetic octapeptide and pentapeptide substrate (N-acetyl Lys-Arg-Tyr-Asn-Leu-Thr-Ser-Val-amide and N-acetyl Lys-Arg-Tyr-Asn-Leu-amide), and enzymatic characteristics were compiled. Early assays on nonamidated forms revealed carboxypeptidase activity, whereas with the amide derivatives no carboxypeptidase activity could be detected. These amide substrates were therefore used in all subsequent incubations. High levels of a Leu/Thr and Lys/Arg cleavage were present in fractions almost throughout the Percoll gradient. Cleavages at Tyr/Asn, Thr/Ser, and Arg/Tyr were localized at different regions of the Percoll gradient. Surprisingly, none of the five enzymatic activities appear to be localized in the secretory granule fractions as defined by the presence of immunoreactive beta-endorphin in the gradient. All of the five proteolytic activities have a basic pH optimum (pH 8-9), and four of them seem to be thiol proteases, as categorized by inhibitor studies. The fifth one, namely the Try/Asn cleavage, is more likely to be due to a metalloendopeptidase, since it is activated by Zn2+ and Co2+.

Animals↗
PubMed1983

Purification of three rat atrial natriuretic factors and their amino acid composition.

A natriuretic factor has been described in the specific granules of rat atria. We have purified three factors which seem to be low-Mr peptides. They have been purified by means of acid extraction, octadecyl Sep-Pak cartridges, and chromatography on Bio-Gel P-10, CM Bio-Gel A, Mono S and reverse-phase high-performance liquid chromatography columns. The factors contain 26, 31 and 33 amino acids and may have been partially degraded during isolation. They are all 3 biologically active and the shorter one is the most active with a specific activity of 450 000 units/mg.

Amino Acids↗
PubMed1983

Characterization of beta-endorphin immunoreactive peptides in rat pituitary and brain by coupled gel and reversed-phase high-performance liquid chromatography.

A procedure which combines gel high-performance liquid chromatography (HPLC) and reversed-phase HPLC in two systems with radioimmunoassay was developed for the analysis of beta-endorphin (beta END)-related peptides in rat pituitary and brain. The gel HPLC system allows rapid screening for relative amounts of precursors and products involved in beta END biosynthesis. Reversed-phase HPLC reveals minor post-translational modifications, such as acetylation, which greatly alter the biological activity of beta END. The application of this coupled procedure clearly demonstrates tissue-specific differences in the processing of beta END in pituitary and brain regions and indicates that the system may be generally applicable to the analysis of neuropeptide heterogeneity.

Animals↗
PubMed1983

Enzymatic maturation of pro-opiomelanocortin by anterior pituitary granules. Methodological approach leading to definite characterization of cleavage sites by means of high-performance liquid chromatography and microsequencing.

The coupling of high-performance liquid chromatography, gel-permeation, and reversed-phase chromatography with microsequencing proved to be advantageous for the unambiguous determination of specific sites in pro-opiomelanocortin, cleaved by secretory granule lysates of pig anterior pituitary. This system allows the unambiguous identification of a major chymotrypsin-like enzyme activity, optimal at pH 8.0, in the granule preparation, with a specificity directed towards some Phe decreases X and Tyr decreases X cleavage sites. The approach used emphasizes the necessity to use methodologies leading to the unambiguous determination of conversion activities.

Amino Acid Sequence↗
PubMed1983

Enzymatic cleavage of pro-opiomelanocortin by anterior pituitary granules. Evidence for a chymotryptic-like enzyme.

This paper presents the results obtained when pig anterior pituitary granule lysates are incubated with rat pro-opiomelanocortin (POMC). The resultant peptides were analyzed by 3 systems of high-performance liquid chromatography. This approach, when coupled with microsequence analysis of the conversion products, allowed the unambiguous identification of a major chymotryptic-like activity (pH optimum around 8) associated with the granule lysates with a specificity directed towards selective Tyr-X and Phe-X bonds within the POMC molecule. Furthermore, these results also demonstrate that although the detected enzyme activity gives rise to products 'resembling' those expected, the characterization of the 'elusive' maturation enzyme responsible for the cleavage at pairs of basic residues remain to be critically evaluated.

Amino Acid Sequence↗
PubMed1983

Primary structure determination of Escherichia coli heat-stable enterotoxin of porcine origin.

The chemical characterization of Escherichia coli heat-stable enterotoxin (ST) is described. The toxin was isolated and purified to homogeneity from the E. coli strain F11 (PI55) of porcine origin. Following quantitative amino acid analysis, the enterotoxin was found to contain 18 amino acids including 6 cysteines, but was devoid of Ser, Val, Met, Ile, Lys, His, and Arg residues. All cysteine residues were found to be involved in disulfide bridges, even though their positions could not be localized. The enterotoxin thus has a molecular weight of 1979 and was shown to be an octadecapeptide with the following sequence: H2N-Asn-Thr-Phe-Tyr-Cys-Cys-Glu-Leu-Cys-Cys-Asn-Pro-Ala-Cys-Ala-Gly-Cys-Tyr- COOH. Its relationship to other known enterotoxins is discussed.

Amino Acid Sequence↗
PubMed1983

Proteases and posttranslational processing of prohormones: a review.

Pioneering work on insulin and on lipotropin, published in 1967, led to the formulation of the hypothesis that biologically active peptides such as peptide hormones are derived from larger precursor molecules by enzymatic cleavage at basic amino acid pairs. Since then, an ever-increasing number of hormones and active peptides including neuropeptides have been found to be contained within the sequence of a larger precursor protein and are released by limited proteolytic cleavage. The hypothesis concerning the posttranslational maturation of precursor molecules into smaller active entities is now firmly established in many tissues (e.g., pituitary gland, pancreas) and for all kinds of organisms (e.g. mammals, fish), though the nature of the enzyme(s) responsible for this maturation process still remains unknown. This article presents current knowledge of the intracellular processing of precursor molecules, especially the conversion of prohormone to hormone. The discussion deals principally with the evidences concerning the localization of the maturation process mainly in the secretory granules, the role of basic amino acid pairs at the cleavage site, and the possible involvement of serine and (or) thiol endopeptidases in that process.

Amino Acid Sequence↗