SEARCH · PubMed Health

Results for “CARBOXYPEPTIDASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10Linked to original sources

PubMed1975

Amino-acid sequence of bovine carboxypeptidase B.

The amino-acid sequence of bovine carboxypeptidase B [peptidyl-L-lysine(-L-arginine)hydrolase, EC 3.4.12.3] has been determined using the heavy and light chains of the enzyme isolated from spontaneously activated pancreatic juice. Comparison of the sequence with that of carboxypeptidase A shows that the two enzymes are homologous (49% identity) and that all but one of the functional residues identified in carboxypeptidase A occur in corresponding loci in carboxypeptidase B (peptidyl-L-amino acid hydrolase, EC 3.4.12.2). The exception is the replacement of Ile-255 at the bottom of the substrate binding pocket of carboxypeptidase A, by aspartic acid in carboxypeptidase B. This single change can account for the difference in specificity of the two enzymes.

Amino Acid Sequence↗

PubMed2005

Pseudomonas aeruginosa LD-carboxypeptidase, a serine peptidase with a Ser-His-Glu triad and a nucleophilic elbow.

LD-Carboxypeptidases (EC 3.4.17.13) are named for their ability to cleave amide bonds between l- and d-amino acids, which occur naturally in bacterial peptidoglycan. They are specific for the link between meso-diaminopimelic acid and d-alanine and therefore degrade GlcNAc-MurNAc tetrapeptides to the corresponding tripeptides. As only the tripeptides can be reused as peptidoglycan building blocks, ld-carboxypeptidases are thought to play a role in peptidoglycan recycling. Despite the pharmaceutical interest in peptidoglycan biosynthesis, the fold and catalytic type of ld-carboxypeptidases are unknown. Here, we show that a previously uncharacterized open reading frame in Pseudomonas aeruginosa has ld-carboxypeptidase activity and present the crystal structure of this enzyme. The structure shows that the enzyme consists of an N-terminal beta-sheet and a C-terminal beta-barrel domain. At the interface of the two domains, Ser(115) adopts a highly strained conformation in the context of a strand-turn-helix motif that is similar to the "nucleophilic elbow" in alphabeta-hydrolases. Ser(115) is hydrogen-bonded to a histidine residue, which is oriented by a glutamate residue. All three residues, which occur in the order Ser-Glu-His in the amino acid sequence, are strictly conserved in naturally occurring ld-carboxypeptidases and cannot be mutated to alanines without loss of activity. We conclude that ld-carboxypeptidases are serine peptidases with Ser-His-Glu catalytic triads.

Alanine↗

PubMed1987

Carboxypeptidase digestion in the presence of detergents.

The detergents, sodium dodecyl sulfate (SDS), lauryl glutamate (LG), and octyl-(polydisperse)oligooxyethylene (Octyl-POE), were tested as to their effects on the activities of carboxypeptidases A, B, and P. In general, Octyl-POE showed little inhibition and SDS showed the strongest inhibition. Carboxypeptidase B was only slightly inhibited by SDS. The inhibitory effect of SDS on these enzyme activities depended not on its concentration but on its absolute amount. For a constant amount of SDS, the activities of carboxypeptidases A and B remained almost constant with increasing reaction volume. Commercial carboxypeptidase B is usually contaminated by carboxypeptidase A. With the addition of SDS, almost only carboxypeptidase B activity was detected.

Carboxypeptidases↗

PubMed1996

Tomato (Lycopersicon esculentum cv. pik-red) leaf carboxypeptidase: identification, N-terminal sequence, stress-regulation, and specific localization in the paraveinal mesophyll vacuoles.

Wounding of tomato (Lycopersicon esculentum L.) leaves causes systemic induction of a serine-type carboxypeptidase activity. We find this activity to be present in several isoforms. Antibodies raised against the leaf carboxypeptidase inhibited the enzyme activity and the immunoprecipitates were resolved into a 69-kDa polypeptide and a doublet of 35/37-kDa proteins on SDS-PAGE. Immunoblot analysis of the leaf proteins also immunodecorated the 69-kDa and 35/37-kDa proteins. Amino acid sequence analysis of the amino-terminus of the tomato leaf 69-kDa carboxypeptidase I [Sorenson et al. (1986) Carlsberg Res. Commun. 51: 475], sharing Ala as the N-terminus and the sequences, AlaProGln and LeuProGlyPhe. Superimposition of a chemical stress (copper treatment) on wounding apparently lowered wound-induced carboxypeptidase activity in the leaf, suggesting that cupric ions might interact with the wound signal. Immunogold electron microscopy indicated that the leaf carboxypeptidase was specifically localized within the inclusions of vacuoles of vascular parenchyma cells. In cupric ion-treated tissues, carboxypeptidase was found redistributed to other parts of the cell, indicating that this treatment, but not wounding, causes general vacuolar membrane damage.

Amino Acid Sequence↗

PubMed1992

Human skin mast cell carboxypeptidase: functional characterization, cDNA cloning, and genealogy.

We functionally characterized human skin mast cell carboxypeptidase A (MC-CPA), and explored its evolutionary relationship to other carboxypeptidases to understand further the structural basis for the substrate preferences of this enzyme. Purified human skin MC-CPA displayed more activity than did bovine pancreatic carboxypeptidase A (CPA) against carboxyl-terminal leucine residues, about equal activity with phenylalanine and tyrosine residues, and no activity with tryptophan or alanine. To correlate kinetic data with structure, we isolated and sequenced a cDNA encoding MC-CPA from human skin, and directly sequenced 30% of the purified protein. These sequences agreed with that of human lung MC-CPA, and further support the evidence for a single MC-CPA gene in humans. Four amino acid replacements, resulting in a net positive change in non-hydrogen atoms in the S1' subsite of MC-CPA, were associated with less alteration in substrate specificity, relative to bovine CPA, than might be expected from studies using rat CPA1 and CPA2. We noted two consensus N-linked glycosylation sites in human MC-CPA that are not found in rat and mouse MC-CPA, or in bovine CPA; that at least one of these sites is glycosylated in vivo was verified by N-glycosidase F treatment, lentil lectin binding, and Concanavalin A-Sepharose chromatography. Evolutionary trees constructed from the known carboxypeptidase sequences suggested that MC-CPA most likely evolved from a carboxypeptidase B-like enzyme, independent of the pancreatic CPA. Thus, in the carboxypeptidase gene family, MC-CPA displays a unique genealogy and several amino acid replacements in its S1' binding pocket that result in substrate specificity quite similar to bovine CPA.

Amino Acid Sequence↗

PubMed1985

Action of serine carboxypeptidases on endopeptidase substrates, peptide-4-methyl-coumaryl-7-amides.

Carboxypeptidase Y hydrolyzed N-substituted peptide-4-methylcoumarin-7-amides (peptide-NH-Mec) at pH 7 by releasing 7-amino-4-methylcoumarin (NH2-Mec) which was then followed by carboxypeptidase action. In particular, a chymotrypsin-directed substrate, Suc-Leu-Leu-Val-Tyr-NH-Mec, was hydrolyzed by the enzyme with a second-order rate constant of 7200 M-1 s-1, which is compatible with the rate for an anilide substrate and some N-substituted dipeptides. The activity was completely inhibited by phenylmethylsulfonyl fluoride and competitively depressed by the presence of an N-substituted dipeptide. Dependences of kinetic parameters on pH were different from those of carboxypeptidase, esterase, amidase, and anilidase activities. Carboxypeptidases P from Penicillium janthinellum and W from wheat also hydrolyzed some of these peptide-NH-Mec derivatives in a similar manner but at a rather low rate. Thus, the NH2-Mec-releasing activity may be considered to be intrinsic to serine carboxypeptidases in general. Taking into consideration this endopeptidase-like activity of serine carboxypeptidases, fluorogenic substrates should be used carefully to specify endopeptidases in crude extracts.

Amino Acids↗

PubMed1991

The vacuolar protein-targeting signal of yeast carboxypeptidase is functional in oocytes from Xenopus laevis.

Carboxypeptidase Y, a yeast vacuolar glycoprotein was expressed in oocytes from Xenopus laevis and its biosynthesis and sorting were examined. In yeast, targeting to the vacuole, the functional equivalent of the lysosome, is not mannose-6-phosphate-receptor dependent. It was found that carboxypeptidase enters the secretory pathway of the oocyte and is there glycosylated, phosphorylated in the carbohydrate part and delivered to the lysosome. Deletion of an amino acid sequence, previously shown to determine intracellular targeting of this enzyme in yeast, caused a loss of phosphorylation and mislocalization of carboxypeptidase Y into the oocyte medium. Inhibition of glycosylation of carboxypeptidase by tunicamycin did not lead to its secretion. In-frame fusion of the targeting domain to a secretory yeast glycoprotein, invertase, did not prevent its secretion. However, a hybrid containing 80% carboxypeptidase abolished invertase secretion. The results indicate that the vacuolar protein-targeting signal from yeast carboxypeptidase can, in principal, function in a higher eukaryote.

Acetylglucosaminidase↗

PubMed1996

Protease inhibitor studies and cloning of a serine carboxypeptidase cDNA from germinating seeds of pea (Pisum sativum L.).

The nature of the proteolytic activity found within the germinating pea (Pisum sativum) seed, 4 days from the initiation of imbibition, was determined by the use of specific protease inhibitors. These studies have shown most of the activity to belong to metallo or metal-activated and serine proteases. In order to investigate further the serine protease activity, a pea cotyledon germination cDNA library was, therefore, screened with a wheat cDNA (2437) [Baulcombe, D.C., Barker, R.F. & Jarvis, M.G. (1987) J. Biol. Chem. 262, 13726-13735] which had extensive similarity to the yeast serine carboxypeptidase Y gene. A positive cDNA clone (pNY551) was obtained which had extensive similarity to the four carboxypeptidases, Arabidopsis thaliana carboxypeptidase Y-like protein, rice serine carboxypeptidase III, barley serine carboxypeptidase III and wheat serine carboxypeptidase III precursor. Northern-blot analysis showed mRNA homologous to pNY551 to be expressed in late developmental pea seed and again during germination.

Amino Acid Sequence↗

PubMed1999

Purification, characterization, and heterologous expression in Fusarium venenatum of a novel serine carboxypeptidase from Aspergillus oryzae.

A novel serine carboxypeptidase (EC 3.4.16.1) was found in an Aspergillus oryzae fermentation broth and was purified to homogeneity. This enzyme has a molecular weight of ca. 67,000, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and its specific activity is 21 U/mg for carbobenzoxy (Z)-Ala-Glu at pH 4.5 and 25 degrees C. It has a ratio of bimolecular constants for Z-Ala-Lys and Z-Ala-Phe of 3.75. Optimal enzyme activity occurs at pH 4 to 4.5 and 58 to 60 degrees C for Z-Ala-Ile. The N terminus of this carboxypeptidase is blocked. Internal fragments, obtained by cyanogen bromide digestion, were sequenced. PCR primers were then made based on the peptide sequence information, and the full-length gene sequence was obtained. An expression vector that contained the recombinant carboxypeptidase gene was used to transform a Fusarium venenatum host strain. The transformed strain of F. venenatum expressed an active recombinant carboxypeptidase. In F. venenatum, the recombinant carboxypeptidase produced two bands which had molecular weights greater than the molecular weight of the native carboxypeptidase from A. oryzae. Although the molecular weights of the native and recombinant enzymes differ, these enzymes have very similar kinetic parameters.

Amino Acid Sequence↗

PubMed2002

Purification and characterization of arginine carboxypeptidase produced by Porphyromonas gingivalis.

Arginine carboxypeptidase was isolated from the cytoplasm of Porphyromonas gingivalis 381 and purified by DEAE-Sephacel column chromatography, followed by high-performance liquid chromatography on DEAE-5PW and TSK G2000SW(XL). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme revealed the presence of three major bands at 42, 33, and 32 kDa with identical N-terminal sequences. By Western blotting analysis and immunoelectron microscopy, the arginine carboxypeptidase was found to be widely distributed in the cytoplasm and on the surface of the outer membrane. The open reading frame corresponding to the N-terminal amino acids of the arginine carboxypeptidase was detected by a search of the sequence of the P. gingivalis W83 genome. This sequence showed homology with mammalian carboxypeptidases (M, N, and E/H) and included a zinc-binding region signature, suggesting that the enzyme is a member of the zinc carboxypeptidase family. The purified enzyme was inhibited by EGTA, o-phenanthroline, DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid, and some metal ions, such as Cu(2+), Zn(2+), and Cd(2+). On the other hand, Co(2+) activated the enzyme. The enzyme released arginine and/or lysine from biologically active peptides containing these amino acids at the C terminus but did not cleave substrates when proline was present at the penultimate position. These results indicate that the arginine carboxypeptidase produced by P. gingivalis is an exo type of metallocarboxypeptidase. This enzyme may function to release arginine in collaboration with an arginine aminopeptidase, e.g., Arg-gingipain, to obtain specific amino acids from host tissues during the growth of P. gingivalis.

3-Mercaptopropionic Acid↗

PubMed1992

Purification and characterization of a developmentally regulated carboxypeptidase from Mucor racemosus.

A developmentally regulated carboxypeptidase was purified from hyphae of the dimorphic fungus Mucor racemosus. The enzyme, designated carboxypeptidase 3 (CP3), has been purified greater than 900-fold to homogeneity and characterized. The carboxypeptidase migrated as a single electrophoretic band in isoelectric focusing polyacrylamide gel electrophoresis (PAGE), with an isoelectric point of pH 4.4. The apparent molecular mass of the native enzyme was estimated by gel filtration to be 52 kDa. Sodium dodecyl sulfate (SDS)-PAGE under nonreducing conditions revealed the presence of a single polypeptide of 51 kDa. SDS-PAGE of CP3 reacted with 2-mercaptoethanol revealed the presence of two polypeptides of 31 and 18 kDa, indicating a dimer structure (alpha 1 beta 1) of the enzyme with disulfide-linked subunits. By using [1,3-3H]diisopropylfluorophosphate as an active-site labeling reagent, it was determined that the catalytic site resides on the small subunit of the carboxypeptidase. With N-carboben zoxy-L-phenylalanyl-L-leucine (N-CBZ-Phe-Leu) as the substrate, the Km, kcat, and Vmax values were 1.7 x 10(-4) M, 490 s-1, and 588 mumol of Leu released per min per mg of protein, respectively. CP3 was determined to be a serine protease, since its catalytic activity was blocked by the serine protease inhibitors diisopropylfluorophosphate, phenylmethylsulfonyl fluoride, and 3,4-dichloroi Socoumarin (DCI). The enzyme was strongly inhibited by the mercurial compound p-chloromercuribenzoate. The carboxypeptidase readily hydrolyzed peptides with aliphatic or aromatic side chains, whereas most of the peptides which contained glycine in the penultimate position did not serve as substrates for the enzyme. Although CP3 activity was undetectable in Mucor yeast cells, antisera revealed the presence of the enzyme in the yeast form of the fungus. The partial amino acid sequence of the carboxypeptidase was determined.

Amino Acid Sequence↗

PubMed2004

Carboxypeptidase-mediated enhancement of nitric oxide production in rat lungs and microvascular endothelial cells.

Membrane-bound regulatory carboxypeptidases cleave only COOH-terminal basic residues from peptides and proteins. To investigate whether carboxypeptidase-generated arginine can increase nitric oxide (NO) synthesis we perfused rat lungs from animals challenged with LPS or used rat lung microvascular endothelial cells (RLMVEC) stimulated with LPS and IFN-gamma, conditions that induced inducible NO synthase (iNOS) expression. Addition of carboxypeptidase substrate furylacryloyl-Ala-Arg (Fa-A-R) or Arg to the lung perfusate increased NO production two- to threefold. The carboxypeptidase inhibitor 2-mercaptomethyl-3-guanidinoethylthiopropanoic acid (MGTA) blocked the effect of Fa-A-R but not free Arg. Lysine, an Arg transport inhibitor, blocked the increase in NO stimulated by Fa-A-R. HPLC analysis showed that Fa-A-R hydrolysis was blocked by MGTA but not lysine. In cytokine-treated RLMVEC, Fa-A-R also stimulated NO production inhibited by MGTA or lysine. Membrane fractions from rat lungs or RLMVEC contained carboxypeptidase M-like activity at neutral pH that increased twofold in RLMVEC treated with LPS + IFN-gamma. The kinetics of NO production in RLMVEC was measured with a porphyrinic microsensor. Addition of 1 mM Arg or Fa-A-R to cells preincubated in Arg-free medium resulted in a slowly rising, prolonged (>20 min) NO output. NO production stimulated by Fa-A-R was blocked by MGTA or iNOS inhibitor 1400W. HPLC analysis of Fa-A-R hydrolysis revealed only 3.7 microM Arg was released over 20 min. Thus NO production in RLMVEC is stimulated more efficiently by Arg released from carboxypeptidase substrates than free Arg. These studies reveal a novel mechanism by which the Arg supply for NO production in inflammatory conditions may be maintained.

Animals↗

PubMed1976

Characterization of proteins from Ascaris lumbricoides which bind specifically to carboxypeptidase.

Inhibitors of the peptidase and esterase activities of carboxypeptidases A and B have been isolated from extracts of Ascaris lumbricoides var suis. These proteins were obtained by treatment of the aqueous extracts at low pH, precipitation with ammonium sulfate, molecular sieving on Bio-Gel P-4, and chromatography on DEAE-cellulose. The inhibitors were resolved into three homogeneous peaks on CM-cellulose. These components, CM-A, CM-B, and CM-C, have constant specific activity and were recovered in a 41% yield. They moved as single bands when subjected to electrophoresis at high or low pH on polyacrylamide gels and they have similar amino acid compositions. Methionine, tyrosine, and cysteine are absent from each of the inhibitors. The 65 residues of CM-B suggest a minimum molecular weight of 7530, in close agreement to the value of 7600 +/- 200 determined on a Bio-Gel P-100 column. Each of the proteins has the same NH2-terminal residues, NH2-Asx-Glx-Val-Glx- and the same COOH-terminal residue, leucine. A plot of per cent acrylamide versus log relative mobility suggests that the three proteins are charge isomers. CM-B appears to be stable to high NaCl concentrations, extremes of pH, high temperatures, and digestion by intestinal proteases. Carboxypeptidase C, carboxypeptidase N, and yeast protease C are not inhibited by CM-B. However, the exopeptidase and esterase activities of human carboxypeptidase A are inhibited. The inhibitors appear to bind to bovine carboxypeptidase A with an atypical stoichiometry. Two moles of CM-B inhibitor bind to 1 mol of enzyme. The evidence is: (a) a demonstrated purity of bovine carboxypeptidase A, (b) minimal and maximal inhibitor molecular weights by different methods, of 7600 and 8300, and (c) a maximum specific activity of apparently homogeneous inhibitors which is 50% of that predicted for unit stoichiometry.

Amino Acids↗

PubMedDate not supplied

[Activity of the basic carboxypeptidases in female rat tissues at different stages of estrus cycle].

It is revealed, that the activity of neuropeptide metabolism enzymes (carboxypeptidase H, phenylmethylsulfonilfluorid-inhibited carboxypeptidase) in the female rat tissues depends upon the stage of estrus cycle. The carboxypeptidase H activity in the pituitary gland is the highest in proestrus; it is almost 3 times higher in comparison with diestrus; it is a little bit higher in striatum on the stage of estrus, than in diestrus and proestrus, in adrenals on the stage of proestrus and estrus it is a little bit lower, than in diestrus; in the ovaries on the stage of proestrus it is much higher, than in estrus and diestrus. The activity of PMSF-inhibited carboxypeptidase in ovaries on the stage of proestrus and diestrus is 1.7-1.8 times higher, than at the stage of diestrus. The activity of carboxypeptidase M in adrenal tissue at the stage of proestrus is 35-40% of that at the stage of diestrus and estrus. The activity of carboxypeptidase M in the ovaries at the stage of diestrus is 45-50% of that at the stage of diestrus and estrus. The role of the investigated enzymes in cyclic changes of a level of biologically active peptides and in regulation of estrus cycle is discussed.

Adrenal Glands↗

PubMed1987

[Isolation and properties of carboxypeptidase from Streptomyces spheroides, strain 35].

Extracellular carboxypeptidase was isolated from culture filtrates of Str. spheroides strain 35, using affinity chromatography on bacitracin-silochrome, bacitracin-Sepharose and CABS-Sepharose. The electrophoretically homogenous enzyme was obtained with a 44% yield and 4160-fold purification. The enzyme-molecular weight is 33,000 Da; pI is 4.7. The amino acid composition of carboxypeptidase is as follows: Asp43, Thr30, Ser35, Glu33, Pro30, Gly47-50, Ala38, 1/2 Cys5-6, Val16, Met2, Ile11, Leu15, Tyr8, Phe10, Lys10, His6, Arg9. The enzyme shows an activity optimum at pH 7.5 is stable at pH 6-8, is completely inhibited with EDTA and can be reactivated by Ca2+. The carboxypeptidase from Str. spheroides strain 35 has a dual substrate specificity, i. e., it splits N-substituted di-, three- and tetrapeptides having both neutral and basic amino acids at the C-ends similar to mammalian carboxypeptidases A and B. The enzyme belongs to the family of metallocarboxypeptidases; its properties are very similar to those of carboxypeptidase S from Str. griseus K-1 and of carboxypeptidase T from Thermoactinomyces sp.

Amino Acids↗

PubMed2002

The p11 subunit of annexin II heterotetramer is regulated by basic carboxypeptidase.

The Ca(2+)-dependent phospholipid-binding protein annexin II heterotetramer (AIIt) is composed of two copies of annexin II and a p11 dimer. The interaction of the carboxyl-terminal lysine residues of the p11 subunit of AIIt with the lysine-binding kringle domains of plasminogen is believed to play a key role in plasminogen binding and stimulation of the tPA-catalyzed cleavage of plasminogen to plasmin. In the current report, we show that AIIt-stimulated plasminogen activation is regulated by basic carboxypeptidases, in vitro. The incubation of AIIt with a 1/400 molar ratio of carboxypeptidase B for periods as short as 2 min resulted in a significant loss in AIIt-stimulated plasminogen activation. Carboxypeptidase B (CpB) as well as thrombin-activated fibrinolysis inhibitor (TAFIa) and carboxypeptidase N (CpN) rapidly reduced AIIt-stimulated plasminogen activation by 80%. The molar ratio of carboxypeptidase/AIIt for half-maximal inhibition of AIIt was 1/4700, 1/700, and 1/500 for CpB, TAFIa, and CpN, respectively. Treatment of AIIt with carboxypeptidase resulted in loss of both carboxyl-terminal lysine residues from the p11 subunit, which correlated with a decrease in the k(cat) and an increase in the K(m) for plasminogen activation. The data reveal a novel mechanism for the regulation of AIIt-stimulated plasminogen activation.

Annexin A2↗

PubMedDate not supplied

Pig platelet acidic carboxypeptidases.

Pig platelet acidic carboxypeptidases hydrolyzed only N-blocked dipeptides with bulky aromatic and aliphatic hydrophobic amino acids. The optimum hydrolysis of these substrates was at pH 5.0. The main acidic carboxypeptidase in pig platelet lysate was lysosomal carboxypeptidase A (1CPA), which hydrolyzed Cbz-Phe-Ala at the highest rate. A lower activity of this enzyme was found on Cbz-Glu-Tyr and Cbz-Glu-Phe. 1CPA also hydrolyzed Cbz-Glu-Tyr at pH 3.5. No activity of lysosomal carboxypeptidase B in platelet lysate was detectable using Bz-Gly-Arg. Pig platelet acidic carboxypeptidase hydrolyzed Cbz-Pro-Phe and Cbz-Pro-Ala, which are specific substrates of lysosomal prolylcarboxypeptidase, more slowly. The incubation of platelet lysate with plasma did not influence the rate of hydrolysis of Cbz-Glu-Tyr, whereas no hydrolysis of Cbz-Pro-Phe was observed.

Animals↗

PubMed1995

Carboxypeptidase M is identical to the MAX.1 antigen and its expression is associated with monocyte to macrophage differentiation.

The two monoclonal antibodies MAX.1 and MAX.11 recognize cell surface antigens that are almost undetectable on monocytes but highly expressed on differentiated macrophages. Biochemical characterization revealed that both antibodies detect the same 58-64-kDa glycoprotein anchored to the plasma membrane by glycosyl-phosphatidylinositol linkage. We purified the MAX.1/11 antigen by immunoaffinity chromatography using monoclonal antibody MAX.11. The NH2-terminal amino acid sequence was determined and turned out to be identical to the NH2-terminal sequence of the membrane-bound carboxypeptidase M. By precipitation with antibodies MAX.1 and MAX.11, membrane preparations of macrophages and placental microvilli were almost completely depleted of enzyme activity, indicating that the two antibodies indeed recognize carboxypeptidase M. Immunoreactivity of both antibodies correlates with the reported tissue distribution of enzyme activity. Expression of carboxypeptidase M on mRNA level and enzymatic activity markedly increase during in vitro differentiation of monocytes, according to the described increase in MAX.1 and MAX.11 antigen expression. Moreover, in vitro differentiated macrophages show the highest specific activity yet described in any tissue. In addition, carboxypeptidase M expression could be detected in HL-60, U937, and THP-1 myeloid cell lines. Vitamin D3-induced monocytic differentiation resulted in an increased carboxypeptidase M expression in all three cell lines. Further studies are needed to elucidate the functional role of carboxypeptidase M during monocytic differentiation and activation.

Antigens, Surface↗