Aminopeptidase in human CSF which degrades delta-sleep inducing peptide (DSIP)

Functional analysis of leucine aminopeptidase in Caenorhabditis elegans

To investigate the function of the enzyme leucine aminopeptidase in nematodes, a Caenorhabditis elegans leucine aminopeptidase gene identified in the genome sequence was functionally analysed by transfection of a leucine aminopeptidase beta-galactosidase reporter construct and characterisation of a null mutant. The leucine aminopeptidase transgene is expressed along the length of the gut, and immunolocalisation shows the enzyme in the buccal cavity, pharynx, anterior gut and rectum. It is constitutively expressed as seen by analysis of cDNAs constructed from mRNAs of nematodes taken at 2 h intervals through the life-cycle; and by western blot analysis of protein from the same set of nematodes. Leucine aminopeptidase null mutants had a slower growth rate and delayed onset of egg-laying. We suggest that in C. elegans, leucine aminopeptidase is a digestive enzyme.

Mass spectrometric analysis of neuropeptidergic systems in the human pituitary and cerebrospinal fluid

Neuropeptidergic systems have been studied in human tissues and fluids, which include the pituitary and lumbar cerebrospinal fluid, respectively. This paper reviews the qualitative and quantitative mass spectrometric analytical data obtained from three areas of study. Methionine enkephalin (ME) and beta-endorphin (BE) were quantified in the human pituitary by liquid secondary ion mass spectrometry (LSI MS)-tandem mass spectrometry. Corresponding stable isotope-incorporated synthetic peptide internal standards were used. Proenkephalin A and proopiomelanocortin produce ME and BE, respectively. The analysis of neuropeptides in macroadenomas demonstrated a decrease in both of those neuropeptidergic systems relative to controls. An analysis of prolactin-secreting microadenomas showed an increase in the proenkephalin A system. Mass spectrometry was also used to detect opioid peptide-containing proteins in the pituitary. Enzymes that process the precursors of proenkephalin A and tachykinin (substance P) neuropeptides were studied in human lumbar cerebrospinal fluid. Electrospray ionization mass spectrometry was used to characterize the molecular mass of each peptide product.

Effects of pH, electric current, and enzyme inhibitors on iontophoresis of delta sleep-inducing peptide

Delta sleep-inducing peptide (DSIP), a peptide of nine amino acid residues, was used as a model drug to investigate the effects of pH, electric current, and enzyme inhibitors on the transdermal iontophoretic delivery of peptide drugs. DSIP was fairly stable in pH 4-9 buffer solutions but was cleaved by the skin enzymes during iontophoretic delivery. Enzyme inhibitors, such as o-phenanthroline, ethylene-diaminetetraacetic acid (EDTA), dilucine, and sodium deoxycholate, could inhibit the degradation of DSIP to a certain extent in the skin homogenate. Our results showed that metalloproteases were probably more important enzymes for DSIP hydrolysis. By using 0.2 mM o-phenanthroline in the iontophoretic delivery of DSIP at pH 4, we were able to significantly enhance the penetration of DSIP. The flux was about eight times as much as control (without o-phenanthroline) at pH 7.4.

cDNA cloning and expression of chicken aminopeptidase H, possessing endopeptidase as well as aminopeptidase activity

Chicken aminopeptidase H is a cysteine protease possessing endopeptidase as well as aminopeptidase activity [Rhyu, M. R., Nishimura, T., Kato, Y., Okitani, A. & Kato, H. (1992) Eur. J. Biochem. 208, 53-59]. This enzyme exhibits molecular masses of 400 kDa on gel filtration and 52 kDa on SDS/PAGE, indicating that it consists of eight subunits with the same molecular mass. In the current study, we cloned the cDNA for the catalytic subunit of chicken aminopeptidase H. The open reading frame of the aminopeptidase H gene consists of 1362 base pairs encoding a 52-kDa protein consistent with the molecular mass determined on SDS/PAGE; the deduced amino acid sequence contains all the partial sequences determined for the purified enzyme. The sequence is similar to that of the bleomycin hydrolase of rabbit lung, which has been partially determined. The recombinant 52-kDa protein expressed in COS7 cells exhibited both aminopeptidase and endopeptidase activities, which were inhibited by monoiodoacetic acid. Furthermore, the expression of aminopeptidase H in COS7 cells was also recognized on immunoblotting. This gene is the first one for aminopeptidase H in an animal tissue whose sequence has been completely determined.

Isolation of bovine kidney leucine aminopeptidase cDNA: comparison with the lens enzyme and tissue-specific expression of two mRNAs

Aminopeptidases catalyze the hydrolysis of amino acid residues from the amino terminus of peptide substrates. Leucine aminopeptidase (LAP) from bovine lens is the best characterized aminopeptidase and the only LAP for which the amino acid sequence was determined by protein sequencing. Using this sequence information, we isolated a bovine kidney LAP cDNA and compared its deduced amino acid sequence to the published amino acid sequence for bovine lens LAP. Overall, the sequences are highly conserved. However, several differences are observed. The kidney LAP cDNA indicates a 26 amino acid extension at the amino terminus which is not found in the mature purified lens LAP. The cDNA also indicates an additional octapeptide in the C-terminal region which was not indicated in the published lens LAP amino acid sequence but which was required for best fit of crystallographic data regarding bovine lens LAP. Several other single amino acid changes were also noted. Levels of LAP transcripts were examined in bovine lens and kidney tissue as well as in cultured lens cells. Lens epithelial tissue showed only one LAP transcript (2.4 kb) whereas two transcripts (2.0 and 2.4 kb) were observed in cultured lens cells derived from epithelial tissue and in kidney tissue. Using Northern blot analysis, we correlated LAP mRNA levels with previously determined changes of LAP activity in aging lens tissue and in progressively passaged lens epithelial cells which were used to simulate aging in vitro. No differences were found in LAP mRNA levels in epithelial tissue from old and young lenses.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the release and metabolism of delta sleep-inducing peptide (DSIP) in the rat brain

In the present study, we examined whether delta sleep-inducing peptide (DSIP) was (1) secreted from neurons on depolarization and (2) degraded by membrane-associated peptidases. Incubation of DSIP with rat brain membrane resulted in the degradation of DSIP with liberation of tryptophan, an N-terminal amino acid of DSIP. Bestatin and puromycin, aminopeptidase inhibitors, significantly inhibited the degradation of DSIP and release of tryptophan. The releases of immunoreactive DSIP-like substance (irDSIP) from rat brain slices and synaptosomes were significantly stimulated by high K(+)-evoked depolarization. The released irDSIP was coeluted with native DSIP on gel filtration chromatography. High K(+)-evoked release of irDSIP did not show extracellular Ca(2+)-dependency. This Ca(2+)-independency suggests that the secretory pathway of DSIP may be different from that of other neurotransmitters. These results demonstrate that DSIP is released from nerve endings on depolarization and inactivated by membrane-associated puromycin-sensitive aminopeptidase. Therefore, DSIP may serve as a neuropeptide-like material in the central nervous systems.

Purification and properties of aminopeptidase H from chicken skeletal muscle

Aminopeptidase H was purified from fresh chicken breast muscle by ammonium sulfate fractionation and successive chromatographies on DEAE-cellulose, Ultrogel AcA 34, activated thiol-Sepharose 4B, phenyl-Sepharose CL-4B and DEAE-cellulose again. The purified enzyme migrated as a single band on SDS/PAGE. Aminopeptidase H exhibits activity against both L-leucine beta-naphthylamide and alpha-N-benzoyl-DL-arginine beta-naphthylamide. The molecular mass of this enzyme was found to be 52 kDa on SDS/PAGE and 400 kDa on Sepharose 6B column chromatography. The optimum pH for the hydrolysis of both substrates was 8.0 and this activity was remarkably enhanced by reducing agents. The enzyme was strongly inhibited by monoiodoacetate and leupeptin, but not affected by EDTA, phenylmethylsulfonyl fluoride, pepstatin, bestatin or puromycin. Aminopeptidase H has been shown to hydrolyze di-, tri- and tetrapeptides in the manner of an aminopeptidase, as well as the beta-naphthylamide derivatives of amino acids. However, the enzyme has not been shown to hydrolyze proteins such as hemoglobin, bovine serum albumin, myofibrillar proteins or sarcoplasmic proteins.

Purification and properties of aminopeptidase C from porcine skeletal muscle

1. Aminopeptidase C was purified from porcine skeletal muscle. 2. The mol. wt of the enzyme was found to be 103,000 on both Sephadex G-200 column chromatography and SDS-PAGE. 3. The optimum pH for the hydrolysis of L-leucine p-nitroanilide was around 7.0. 4. The activity of this enzyme was strongly inhibited by EDTA, bestatin and puromycin. 5. The enzyme acted on the beta-naphthylamide derivatives of amino acids and oligopeptides.

Analysis of proenkephalin A, proopiomelanocortin and protachykinin neuropeptides in human lumbar cerebrospinal fluid by reversed-phase high-performance liquid chromatography, radioimmunoassay and enzymolysis

A comprehensive high-performance liquid chromatographic, radioimmunoassay, and enzymatic degradation scheme has been developed to analyze several intact neuropeptides and the corresponding peptides created by in vivo enzymolysis of precursors to study neuropeptides in human lumbar cerebrospinal fluid (CSF) and to test the hypothesis that defects in the metabolism (synthesis, degradation) of neuropeptide precursors, neuropeptides, and metabolites play a role in low back pain. CSF samples were obtained from three different patient groups: controls (C), whose low back pain was relieved without lidocaine; pharmacological responders (PR), whose pain was relieved by lidocaine and who were candidates for surgery; and pharmacological non-responders (PNR), whose pain was not relieved by lidocaine and a mid-thoracic anesthetic, and who were not candidates for surgery. The metabolic activity involved during synthesis and degradation of the peptides was assessed by measuring intact, native neuropeptide immunoreactivity in pre-incubated and post-incubated CSF samples, where samples were incubated at 37 degrees C for 1 h. Pre-incubation radioimmunoassay measurements reflected the content of intact peptides present in lumbar CSF at the time of sampling, and post-incubation measurements assayed the amount of peptide that had remained embedded within its precursors [cryptic methionine enkephalin (ME)] and that had been released by the action of CSF peptidases. Significant differences were found in post-incubation samples for the amount of proenkephalin A [ME, leucine enkephalin (LE)] and tachykinin [substance P (SP)] peptides. For example, significant differences were observed for ME-like immunoreactivity (C versus cryptic), SP-like immunoreactivity (PNR versus PR), and LE-like immunoreactivity (PR versus C). No significant differences were observed among the peptides within the pre-incubation samples.(ABSTRACT TRUNCATED AT 250 WORDS)