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PubMed1994

The regional distribution of N-acetylaspartylglutamate (NAAG) and peptidase activity against NAAG in the rat nervous system.

N-Acetylaspartylglutamate (NAAG), a prevalent peptide in the vertebrate nervous system, may be hydrolyzed by extracellular peptidase activity to produce glutamate and N-acetylaspartate. Hydrolysis can be viewed as both inactivating the peptide after synaptic release and increasing synaptic levels of ambient glutamate. To test the hypothesis that NAAG and the peptidase activity that hydrolyzes it coexist as a unique, two-stage system of chemical neurotransmission, 50 discrete regions of the rat CNS were microdissected for assay. In each microregion, the concentration of NAAG was determined by radioimmunoassay and the peptidase activity was assayed using tritiated peptide as substrate. The NAAG concentration ranged from 2.4 nmol/mg of soluble protein in median eminence to 64 in thoracic spinal cord. Peptidase activity against NAAG ranged from 54 pmol of glutamate produced per milligram of membrane protein per minute in median eminence to 148 in superior colliculus. A linear relationship was observed between NAAG peptidase and NAAG concentration in 46 of the 50 areas, with a slope of 2.26 and a correlation coefficient of 0.45. These data support the hypothesis that hydrolysis of NAAG to glutamate and N-acetylaspartate is a consistent aspect of the physiology and metabolism of this peptide after synaptic release. The ratio of peptide concentration to peptidase activity was > 0.3 in the following four areas: ventrolateral medulla and reticular formation where the peptide is concentrated in axons of passage, thoracic spinal cord, where NAAG is concentrated in ascending sensory tracts as well as motoneuron cell bodies, and ventroposterior thalamic nucleus.

Animals↗
PubMed1994

Cholinesterases display genuine arylacylamidase activity but are totally devoid of intrinsic peptidase activities.

The purpose of this article was to evaluate the intrinsic character of arylacylamidase and peptidase activities that are often detected along with cholinesterase activities. Various pools of commercial or affinity-purified acetylcholinesterases (AChEs) were examined. Affinity-purified AChE displays esterase- and amidase-specific activities that are similarly enriched when compared with commercial AChE. By contrast, commercial AChE exhibits much higher tryptic-like and carboxypeptidase-specific activities than the affinity-purified enzyme. The parallel enrichment in esterase and arylacylamidase suggests that these two activities are copurified, whereas peptidases do not seem to behave similarly. We show that trypsinolysis or spontaneous degradation of affinity-purified AChE leads to the conversion of the 75-kDa monomer protein into two fragments of 50 and 25 kDa after sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. However, these modifications are without effect on the esterase, arylacylamidase, and peptidase activities. This clearly shows that AChE does not behave as a zymogen of peptidases that would have been activated on autolysis of AChE. Immunoprecipitation of AChEs with a purified monoclonal antibody directed toward electric eel AChE totally separated the esterase and arylacylamidase activities (pellet) from peptidase activities (supernatant). The immunoprecipitated AChEs could be dissociated from the interaction with IgGs. These resolubilized AChE preparations have kept the same percentage of initial esterase and arylacylamidase activities but were totally devoid of peptidase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1997

Molecular cloning of a peptidase against N-acetylaspartylglutamate from a rat hippocampal cDNA library.

N-Acetylaspartylglutamate (NAAG) is the most prevalent peptide neurotransmitter in the mammalian nervous system. NAAG selectively activates the type 3 metabotropic glutamate receptor. It is inactivated by peptidase activity on the extracellular face of the plasma membrane of neurons and glia. The human gene that codes for prostate-specific membrane antigen (PSM) has been shown to produce peptidase activity against NAAG. We cloned the human PSM cDNA and used it to probe a rat hippocampal cDNA library. We identified a cDNA containing a complete coding region that possesses 83% homology with the PSM gene. The predicted 752-amino acid sequence has 85% identity and 91% similarity to the PSM sequence. CHO cells transfected with this cDNA expressed NAAG peptidase activity at a level similar to that obtained from rat brain membranes. The peptidase activity was inhibited by beta-NAAG, quisqualate, and pteroylglutamate but not aspartylglutamate or pteroic acid. In situ hybridization data demonstrated the widespread distribution of the peptidase mRNA in the brain, consistent with the distribution of peptidase activity. The highest levels of hybridization were detected in the hippocampus, dentate gyrus, piriform cortex, choroid plexus of the ventricles, pineal gland, anterior pituitary, and supraoptic nucleus. Three transcripts (estimated at 5, 3.4, and 2.9 kb) were identified in northern blots of rat brain, while in rat kidney the third transcript appeared slightly smaller than 2.9 kb. With use of reverse transcriptase PCR with primers for the 5' end, the central region, and the 3' end of the hippocampal cDNA, the expected amplification products were obtained from rat brain RNA. Spinal cord yielded an amplification product only with primers for the 5' end of the hippocampal cDNA.

Amino Acid Sequence↗
PubMed2007

The crystal structure of the rhomboid peptidase from Haemophilus influenzae provides insight into intramembrane proteolysis.

Rhomboid peptidases are members of a family of regulated intramembrane peptidases that cleave the transmembrane segments of integral membrane proteins. Rhomboid peptidases have been shown to play a major role in developmental processes in Drosophila and in mitochondrial maintenance in yeast. Most recently, the function of rhomboid peptidases has been directly linked to apoptosis. We have solved the structure of the rhomboid peptidase from Haemophilus influenzae (hiGlpG) to 2.2-A resolution. The phasing for the crystals of hiGlpG was provided mainly by molecular replacement, by using the coordinates of the Escherichia coli rhomboid (ecGlpG). The structural results on these rhomboid peptidases have allowed us to speculate on the catalytic mechanism of substrate cleavage in a membranous environment. We have identified the relative disposition of the nucleophilic serine to the general base/acid function of the conserved histidine. Modeling a tetrapeptide substrate in the context of the rhomboid structure reveals an oxyanion hole comprising the side chain of a second conserved histidine and the main-chain NH of the nucleophilic serine residue. In both hiGlpG and ecGlpG structures, a water molecule occupies this oxyanion hole.

Animals↗
PubMed1987

N-terminal methionine-specific peptidase in Salmonella typhimurium.

Crude extracts of a multiply peptidase-deficient strain of Salmonella typhimurium contain an aminopeptidase that specifically removes N-terminal methionine from peptides. This activity shows pronounced specificity for the peptide's second amino acid. Methionine is removed from peptides with alanine, threonine, or glycine in this position but not when the second amino acid is leucine or methionine. The activity is stimulated by Co2+ and is inhibited by EDTA. Mutations that lead to overproduction (up to 30-fold) of the activity have been obtained by selecting for growth on Met-Gly-Gly as a methionine source. These mutations map at approximately 3 map units, phage P22 cotransducible with leu. The overproducer mutations are dominant to wild type, and duplication of the wild-type allele of the locus leads to a gene dosage effect on peptidase levels. This suggests that the locus of the overproducer mutations may be the structural gene for the peptidase. NaDodSO4/PAGE shows an increased level of a single protein (34 kDa) in the overproducer mutant. This protein is highly enriched in a purified preparation of the peptidase. The specificity of this enzyme suggests that it is involved in the cleavage of methionine from newly synthesized peptide chains. This activity can specifically remove methionine from the N terminus of a completed protein. Treatment of purified, unprocessed (N-terminal methionine) interleukin 1 beta with the purified peptidase results in removal of N-terminal methionine with no additional alterations. N-terminal processing of at least this protein can occur after translation is complete. We propose to call this enzyme peptidase M (methionine-specific aminopeptidase).

Amino Acid Sequence↗
PubMed1995

A mutation affecting signal peptidase inhibits degradation of an abnormal membrane protein in Saccharomyces cerevisiae.

Signal peptidase removes amino-terminal signal peptides from precursor proteins during or immediately following their translocation to the lumen of the endoplasmic reticulum (ER) and may participate in ER degradation, a poorly defined process whereby abnormal proteins are rapidly degraded early in the secretory pathway. Here, the involvement of signal peptidase in ER degradation is examined through the use of two chimeric membrane proteins that lack amino-terminal signal peptides: A189invHD, which contains sequences derived from arginine permease and histidinol dehydrogenase, and AHDK2, containing the ER-resident protein Kar2p fused to the carboxyl terminus of A189invHD. Degradation of approximately 95% of A189invHD is observed in yeast cells expressing enzymatically active signal peptidase, whereas only 60% undergoes rapid degradation in a sec11 mutant bearing a temperature-sensitive mutation in the gene encoding the 18-kDa subunit (Sec11p) of the signal peptidase complex. AHDK2 is proteolyzed in a reaction yielding at least two fragments in wild-type cells and in the sec11 mutant containing a plasmid bearing the SEC11 gene. The proteolytic reaction is catalyzed in a temperature-dependent manner in the sec11 mutant, with AHDK2 remaining stable at the nonpermissive temperature. Using conditional mutants defective in protein translocation into and out of the ER and in vitro protease protection studies, the site of degradation for AHDK2 is localized to the ER lumen. The data therefore indicate (i) A189invHD is degraded through both signal peptidase-dependent and independent processes; (ii) signal peptidase, specifically the Sec11p subunit, is required for the proteolysis of AHDK2; and (iii) the Kar2 fragment at the carboxyl terminus of AHDK2 permits detection of proteolytic intermediates.

Alcohol Oxidoreductases↗
PubMed1996

Selective monitoring of peptidase activities with synthetic polypeptide substrates and polyion-sensitive membrane electrode detection.

A novel method to monitor specific peptidase activities in biological samples as complex as undiluted plasma/blood is described. The approach is based on the design of synthetic polypeptide substrates in which di- or triarginine sequences are linked to each other via one or more other amino acids recognized specifically by the peptidase to be determined. Detection of chymotrypsin and renin activities using synthetic substrates P4 (F-R-R-R-F-V-R-R-F-NH2) and P5 (R-R-R-L-L-R-R-L-L-R-R-R), respectively, serves to demonstrate the principles of this new assay system. A polyion-sensitive membrane electrode, prepared by doping polymer films with dinonylnaphthalene-sulfonate (DNNS), is shown to exhibit significant nonequilibrium electromotive force (EMF) responses toward these and other polycationic substrates at microgram/milliliter levels under physiological conditions. The same electrode, however, exhibits much smaller total EMF response toward the shorter fragments of the synthetic peptides generated by peptidase activity; hence, the addition of peptidase to a solution containing the synthetic substrate yields a change in electrode EMF response, the rate of which is proportional to the activity of peptidase present. Other synthetic polycationic peptides as well as natural polycationic peptides (e.g., protamine) that lack specific cleavage sites for chymotrypsin and renin, yet are detected by the DNNS-based membrane electrode, do not elicit any significant change in EMF response in the presence of the peptidases, confirming the feasibility and utility of the proposed bioanalytical method.

Amino Acid Sequence↗
PubMed1979

Developmental expression of genetically defined peptidases in maize.

The activities of genetically defined amino- and endopeptidases of maize were compared in pericarp, endosperm, and embryonic tissue of the maize kernel from 5 days postpollination until harvest. Activities were highest in the immature stages and declined as drying progressed. The expression of some of the peptidase genes contributed by the pollen parent was examined during early endosperm development in an F(1) cross. The paternally contributed peptidase variants could first be detected 7 days after pollination.During germination and early seedling growth the peptidase activities continued to decline in the endosperm but maintained high levels in the scutellum. The maize peptidases probably have no direct role in hydrolysis of endosperm storage proteins during germination and growth.The peptidase isozymes were associated with the soluble cytoplasmic fraction of the maize scutellum during early growth. Only one tissue specificity was found for the peptidases. Occurrence of a particular aminopeptidase isozyme, AMP2, is limited to endosperm tissue during kernel maturation.

Journal Article↗
PubMed2006

Proteasomal chymotrypsin-like peptidase activity is required for essential functions of human monocyte-derived dendritic cells.

The ubiquitin-proteasome pathway is the principal system for extralysosomal protein degradation in eukaryotic cells, and is essential for the regulation and maintenance of basic cellular processes, including differentiation, proliferation, cell cycling, gene transcription and apoptosis. The 26S proteasome, a large multicatalytic protease complex, constitutes the system's proteolytic core machinery that exhibits different proteolytic activities residing in defined proteasomal subunits. We have identified proteasome inhibitors - bortezomib, epoxomicin and lactacystin - which selectively inhibit the proteasomal beta5 subunit-located chymotrypsin-like peptidase activity in human monocyte-derived dendritic cells (DCs). Inhibition of proteasomal chymotrypsin-like peptidase activity in immature and mature DCs impairs the cell-surface expression of CD40, CD86, CD80, human leucocyte antigen (HLA)-DR, CD206 and CD209, induces apoptosis, and impairs maturation of DCs, as demonstrated by decreased cell-surface expression of CD83 and lack of nuclear translocation of RelA and RelB. Inhibition of chymotrypsin-like peptidase activity abrogates macropinocytosis and receptor-mediated endocytosis of macromolecular antigens in immature DCs, and inhibits the synthesis of interleukin (IL)-12p70 and IL-12p40 in mature DCs. As a functional consequence, DCs fail to stimulate allogeneic CD4(+) and CD8(+) T cells and autologous CD4(+) T cells sufficiently in response to inhibition of chymotrypsin-like peptidase activity. Thus, proteasomal chymotrypsin-like peptidase activity is required for essential functions of human DCs, and inhibition of proteasomal chymotrypsin-like peptidase activity by selective inhibitors, or by targeting beta5 subunit expression, may provide a novel therapeutic strategy for suppression of deregulated and unwanted immune responses.

Acetylcysteine↗
PubMed1995

Evidence for a catalytic role of tyrosine 383 in the peptidase reaction of leukotriene A4 hydrolase.

Leukotriene A4 (LTA4) hydrolase is a bifunctional zinc metalloenzyme which catalyzes the final step in the biosynthesis of the proinflammatory leukotriene B4 and which also possesses a peptidase activity. From sequence comparisons with aminopeptidases, a tyrosine at position 383 in LTA4 hydrolase has been suggested as a possible catalytic amino acid. To explore the potential role of this amino acid in catalysis, we replaced the tyrosine residue with phenylalanine, histidine or glutamine residues by site-directed mutagenesis. The mutated cDNAs were expressed in Escherichia coli and the resulting recombinant proteins, named [Y383F]LTA4 hydrolase, [Y383H]LTA4 hydrolase and [Y383Q]LTA4 hydrolase, were purified to homogeneity to allow assays of both the epoxide hydrolase activity, i.e. the conversion of LTA4 into leukotriene B4, and the peptidase activity. None of the mutated proteins exhibited significant peptidase activities, all of them showing activities less than 0.3% that of the wild-type enzyme. The epoxide hydrolase activity was not affected to the same degree and corresponded to 11, 16 and 17% that of the unmutated enzyme for [Y383F]LTA4 hydrolase, [Y383H]LTA4 hydrolase and [Y383Q]LTA4 hydrolase, respectively. Kinetic analysis was performed with the mutant [Y383Q]LTA4 hydrolase, which revealed an approximately 10-fold increase in Km for leukotriene A4 compared to that for the unmutated enzyme. At high concentrations of substrate, the difference in enzyme velocity was only moderate, with Vmax values of 600 nmol.mg-1.min-1 and 1000 nmol.mg-1.min-1 for [Y383Q]LTA4 hydrolase and the wild-type enzyme, respectively. No such effect of substrate concentration could be observed on the peptidase activity. As a positive control, we exchanged a glycine residue in position 386 for an alanine residue, and the recombinant protein, [G386A]LTA4 hydrolase retained 19% and 77% of the peptidase and epoxide hydrolase activities, respectively. The results from this study are consistent with a role for Tyr383 in the peptidase reaction of LTA4 hydrolase, where it may act as a proton donor in a general base mechanism. However, our data do not allow a similar interpretation for the mechanism involved in the hydrolysis of LTA4 into LTB4.

Amino Acid Sequence↗
PubMed1983

Demonstration by a novel genetic technique that leader peptidase is an essential enzyme of Escherichia coli.

It was previously shown that two separate regions of DNA are required for expression of the cloned leader peptidase gene on plasmid pTD101 (T. Date and W. Wickner, Proc. Natl. Acad. Sci. U.S.A. 78:6106-6110, 1981). Both loci have been mapped in detail, and their roles have been established. A 1.3-kilobase region, termed the L region, encodes the 37,000-dalton leader peptidase protein. Another region, termed the P region, is about 1.5 kilobases away from the L region and is less than 350 base pairs long. The P region acts in cis to the L region, suggesting that it plays a role as a promoter. A technique for inactivation of the leader peptidase gene on the Escherichia coli chromosome has been developed to examine whether the leader peptidase which we had cloned is essential for cell growth. A specific plasmid (P(-) L(-)) which deletes both the P region and a substantial portion of the L region was constructed and transformed into a polA mutant strain. The plasmid cannot replicate in this strain; thus, the plasmid-borne ampicillin resistance is lost unless the plasmid DNA recombines into the chromosome. Integration of the P(-) L(-) plasmid did not yield any viable ampicillin-resistant cells, whereas the three control plasmids, P(+) L(+), P(+) L(-), and P(-) L(+), did. When the P(-) L(-) plasmid was transformed into the polA(Ts) strain, the strain could only grow in the presence of ampicillin at a permissive temperature, suggesting that integration of the plasmid into the host chromosome leads to inactivation of the chromosomal leader peptidase gene. Southern hybridization analysis demonstrated that the integration of plasmids into the chromosome occurred at the homologous site. This study demonstrates that expression of the leader peptidase gene is critical for cell growth.

Chromosome Mapping↗
PubMed1996

Multiple-peptidase mutants of Lactococcus lactis are severely impaired in their ability to grow in milk.

To examine the contribution of peptidases to the growth of lactococcus lactis in milk, 16 single- and multiple-deletion mutants were constructed. In successive rounds of chromosomal gene replacement mutagenesis, up to all five of the following peptidase genes were inactivated (fivefold mutant): pepX, pepO, pepT, pepC, and pepN. Multiple mutations led to slower growth rates in milk, the general trend being that growth rates decreased when more peptidases were inactivated. The fivefold mutant grew more than 10 times more slowly in milk than the wild-type strain. In one of the fourfold mutants and in the fivefold mutant, the intracellular pools of amino acids were lower than those of the wild type, whereas peptides had accumulated inside the cell. No significant differences in the activities of the cell envelope-associated proteinase and of the oligopeptide transport system were observed. Also, the expression of the peptidases still present in the various mutants was not detectably affected. Thus, the lower growth rates can directly be attributed to the inability of the mutants to degrade casein-derived peptides. These results supply the first direct evidence for the functioning of lactococcal peptidases in the degradation of milk proteins. Furthermore, the study provides critical information about the relative importance of the peptidases for growth in milk, the order of events in the proteolytic pathway, and the regulation of its individual components.

Amino Acid Sequence↗
PubMed2000

A truncated soluble Bacillus signal peptidase produced in Escherichia coli is subject to self-cleavage at its active site.

Soluble forms of Bacillus signal peptidases which lack their unique amino-terminal membrane anchor are prone to degradation, which precludes their high-level production in the cytoplasm of Escherichia coli. Here, we show that the degradation of soluble forms of the Bacillus signal peptidase SipS is largely due to self-cleavage. First, catalytically inactive soluble forms of this signal peptidase were not prone to degradation; in fact, these mutant proteins were produced at very high levels in E. coli. Second, the purified active soluble form of SipS displayed self-cleavage in vitro. Third, as determined by N-terminal sequencing, at least one of the sites of self-cleavage (between Ser15 and Met16 of the truncated enzyme) strongly resembles a typical signal peptidase cleavage site. Self-cleavage at the latter position results in complete inactivation of the enzyme, as Ser15 forms a catalytic dyad with Lys55. Ironically, self-cleavage between Ser15 and Met16 cannot be prevented by mutagenesis of Gly13 and Ser15, which conform to the -1, -3 rule for signal peptidase recognition, because these residues are critical for signal peptidase activity.

Amino Acid Sequence↗
PubMed1999

Membrane-bound cell surface peptidases in reproductive organs.

Membrane-bound cell surface peptidases including aminopeptidase-N (EC 3.4.11.2), dipeptidyl peptidases IV (EC.3.4.14.5), carboxypeptidase-M (EC 3.4.17.12), neutral endopeptidase (EC 3.4.24.11) and endothelin converting enzyme-1 (EC 3.4.23) were shown to be differently expressed on human ovarian granulosa, theca interna and luteal cells and on endometrial epithelial and stromal cells. These peptidases have their catalytic sites extracellularly and can metabolize biologically active peptides at the cell surface, serving as local regulators of peptide concentrations. In the ovary and endometrium, numerous peptides are considered to be locally produced and play an important role in the follicular growth, ovulation, corpus luteum function, endometrial differentiation and embryo implantation in an autocrine and/or paracrine fashion. The inhibition of aminopeptidase activity by bestatin affected murine follicular growth, steroidogenesis by porcine ovarian cells and progesterone-induced decidualization of human endometrial stromal cells in vivo or in vitro. These findings suggest that membrane-bound peptidases are important regulators of the function and differentiation of the ovarian cells and endometrial cells including embryo. In the near future, the physiological roles of these peptidases will be clarified and clinical use of peptidase inhibitors may be applied to the various reproductive disorders.

Animals↗
PubMed1979

Comparison of two pig intestinal brush border peptidases with the corresponding renal enzymes.

Intestinal dipeptidyl peptidase IV and gamma-glutamyltransferase were compared to the corresponding kidney enzymes with respect to immunological and electrophoretic properties. The influences of selected effectors on the two enzymes were also studied. The two kidney peptidases exhibited the reaction of total identity with the corresponding intestinal enzymes in immunodiffusion. Furthermore, the intestinal dipeptidyl peptidase IV and gamma-glutamyl transferase showed the same inhibition patterns as the corresponding kidney enzymes and the acceptor specificity of the intestinal gamma-glutamyl-transferase was found to be identical to that of the kidney enzyme. The electrophoretic mobilities of dipeptidyl peptidase IV from the two organs differed greatly. The difference was almost abolished by treatment with neuraminidase, suggesting that the variation in mobility was due to different contents of sialic acid. It is suggested that the intestinal brush border peptidases, dipeptidyl peptidase IV and gamma-glutamyltransferase, are closely related to the corresponding enzymes obtained from the kidney.

Animals↗
PubMed2002

The peptidase zymogen proregions: nature's way of preventing undesired activation and proteolysis.

Since the initial description of a peptidase activity, namely pepsin, in the middle of the 19(th) century, our understanding of the molecular basis of peptidase function and activation has greatly improved. Further, by sequencing entire genomes, we have reached a stage whereby it is now possible to appreciate the tremendous diversity and unique specificities of peptidases. Because of their importance in most if not all vital processes of the cell including ultimately its death, their activities must be carefully localized and kept under tight control. In addition to endogenous inhibitors, control of enzymatic activity can be achieved through their synthesis and transport as inactive zymogens. This review article will focus on the characteristics as well as the role of the proregion contained within the peptidase zymogen structure. It will survey novel zymogen structures determined in the past 5 years as well as those of selected emerging peptidase families for which there exists as yet no or little structural data. These include members belonging to the caspase, ADAMS, TTSP, MMP, Aspartyl peptidases and convertase families.

Enzyme Activation↗
PubMed1980

Peptidase activities in the functioning jejunum and ileum before and after jejunoileal bypass in morbid obesity.

Different peptidase activities were studied preoperatively and postoperatively on intestinal biopsy specimens from patients with jejunoileal bypass for morbid obesity. Preoperatively the activities of the brush border peptidases, microvillus aminopeptidase (EC 3.4.11.2) and dipeptidyl peptidase IV (EC 3.4.14.X), were lowest at the ligament of Treitz and highest in the distal ileum. The activity of the other brush border peptidase studied, the gamma-glutamyl transpeptidase (EC 2.3.2.2), had a maximum at proximal jejunum, like the two cytosol dipeptidases glycyl-leucine dipeptidase (EC 3.4.13.2) and proline dipeptidase (EC 3.4.13.9). Postoperative changes in peptidase activities were most pronounced in the ileal part of the shunt, whereas changes were small in the jejunal part. The most conspicuous finding was a significant increase in gamma-glutamyl transpeptidase activity in the ileum. There was also tendency to an increase of the cytosol dipeptidases in the ileum. In contrast, the activity of microvillus aminopeptidase and dipeptidyl peptidase IV in the ileum had a tendency to decrease.

Adult↗
PubMed1993

Serum collagenase-like peptidase activity correlated with bone mineral density. A study of 102 elderly women.

To clarify the relationship between collagenase-like peptidase (CL-peptidase) and bone metabolism, serum CL-peptidase activity and bone mineral density (BMD) in the lumbar spine, measured by dual energy X-ray absorptiometry (DEXA), were determined in 102 women with a mean age of 70 (41-94) years. The serum activity of CL-peptidase increased slightly with age up to the 8th decade, and then decreased. Next, we classified the subjects into the following 2 groups by age: a postmenopausal group 50-69 years, and an elderly group over 70 years. In the younger group serum CL-peptidase activity did not correlate with BMD, while in the elderly it did. Our result suggests that serum CL-peptidase activity may reflect bone resorption in elderly women.

Adult↗