Carboxypeptidase Y in sequence determination of peptides

Two adrenal opioid polypeptides: proposed intermediates in the processing of proenkephalin

Two enkephalin-containing polypeptides of 3600 and 4900 daltons have been isolated from extracts of bovine adrenal medulla, purified to homogeneity, and analyzed by a combination of automated Edman degradation and enzymatic time course hydrolysis. The 4900-dalton polypeptide contains two copies of enkephalin, one an internal [Met]enkephalin sequence, the other a [Leu]enkephalin sequence at the carboxyl terminus. Sequence analysis of the 3600-dalton polypeptide has not been completed, but the polypeptide has been shown to contain a single [Met]enkephalin sequence followed by an -Arg-Phe linkage that forms the carboxyl terminus of the molecule. On the basis of these and other findings, we propose that the above enkephalin-containing polypeptides are intermediates in the biosynthesis of the enkephalins and that they are generated by posttranslational processing from a large multivalent enkephalin precursor molecule, proenkephalin. The term "multivalent" is used to indicate a polypeptide with many identical functional sequences.

Identification of dermorphin and Hyp6-dermorphin in skin extracts of the Brazilian frog Phyllomedusa rhodei

Methanol extracts of the skin of the Brazilian frog Phyllomedusa rhodei contain approximately equal amounts of dermorphin and its analogue Hyp6-dermorphin, two opiate-like heptapeptides. A unique feature of their sequence is the presence of a D-amino acid residue at position 2. Hyp6-dermorphin possesses a spectrum of central and peripheral bioactivity very similar to that of dermorphin.

Primary structure of the Fc region of human immunoglobulin D: implications for evolutionary origin and biological function

We have determined the complete amino acid sequence of a tryptic Fc delta fragment generated from an intact human IgD (WAH); it is 226 residues long and includes the second (C delta 2) and the third (C delta 3) constant domains of the delta chain. Comparison of the homology of the Fc sequence of the five human immunoglobulin classes suggests that either the delta-chain gene evolved from the alpha-chain gene soon after the divergence of a mu-alpha common ancestor or it evolved from an ancestral gene distinct from both the mu-alpha and the gamma-epsilon common ancestors. Comparative study using a spatial model of the Fc region indicates that the structure of the C delta 3 domain differs extensively from that of the carboxy-terminal domains of other heavy chain classes; this, together with the unique hinge region structure, probably reflects the biological role of IgD as a receptor molecule on the B-lymphocyte surface.

Studies on aspartase. VI. Trypsin-mediated activation releasing carboxy-terminal peptides

Aspartase (L-aspartate ammonia-lyase, EC 4.3.1.1) of Escherichia coli, already of full activity, is 3-5-fold activated by a limited proteolysis with trypsin (Mizuta, K. and Tokushige, M. (1976) Biochim. Biophys. Acta 452, 253-261). Structural bases for the activation were investigated. The NH2-termini of the native enzyme and of the trypsin-activated enzyme were found to be equally serine, as analyzed by the dansylation method. However, the COOH-terminal glutamate of the native enzyme was altered to arginine upon activation, as revealed by treatments with carboxypeptidases Y, A and B. The released peptides were obtained by molecular sieve membrane filtration following trypsin activation of the enzyme. The peptides were separated by high voltage paper electrophoresis, and the amino acid composition and the terminal residues were determined. The results showed that one or a few related peptides consisting of 7-17 residues were released from the COOH-terminal upon activation. The circular dichroism spectrum of the enzyme suggested that the helical content of the activated enzyme was about 5% less than that of the native enzyme, an indication that the trypsin-activated enzyme has a somewhat looser conformation than the native enzyme. Determination of the fluorescence decay time of the enzyme protein indicated that the tryptophan residue became more exposed to outer environment than that of the native enzyme upon trypsin-activation.

Superoxide dismutase from Bacillus stearothermophilus. Complete amino acid sequence of a manganese enzyme

Superoxide dismutase from the thermophilic bacterium Bacillus stearothermophilus is dimeric with a molecular weight of 45 487. It contains one atom manganese(III) per dimeric molecule [Brock, C. J., Harris, J. I., & Sato, S. (1976) J. Mol. Biol. 107, 175-178]. The subunits are identical, and the following primary structure comprising 203 amino acids has been determined: (Formula: see text) The enzyme is identical in 60% of its residues with the Escherichia coli B manganese enzyme [Steinman, H. M. (1978) J. Biol. Chem 253, 8708-8720]. Neither manganese enzyme has significant homology with the Cu/Zn superoxide dismutase from bovine erythrocytes. The secondary structures of the manganese enzymes predicted by McLachlan's method [McLachlan, A. D. (1977) Int.J. Quantum chem. 12, 371-385] indicate that the eight-stranded beta barrel of the Cu/Zn enzyme [Richardson, J.S., Thomas, K. A., Byron, H. R., & Richardson, D. C. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 1349-1353] is absent from the manganese enzymes.

Mechanistic studies of carboxypeptidase Y from Saccharomyces cerevisiae. pH and pD profiles and inactivation at low pH (pD) values

Steady-state kinetics of carboxypeptidase Y, a proteinase from yeast, were studied by using the reaction of 4-nitrophenyl trimethylacetate as a probe. The pH profile of kcat. is sigmoidal in H2O-based buffers for the carboxypeptidase Y-catalysed hydrolysis of this ester (kcat. referring to the rate of deacylation of trimethylacetyl-carboxypeptidase Y). The corresponding pD profile in 2H2O is doubly sigmoidal, with inflexions at pD approximately 3.8 and approximately 6.8. The ionization of pKDapp. approximately 3.8 is caused by a rapid inactivation in 2H2O media by a process that is only slowly reversed on transfer to pH 7.00 phosphate buffer in H2O. The corresponding inactivation in H2O-based buffers of low pH is considerably slower (approximately 30-fold), follows a first-order rate-dependence and is very strongly pH-dependent, indicating some form of co-operative change in enzyme tertiary structure.

Purification and primary structure of two neuroactive peptides that cause bag cell afterdischarge and egg-laying in Aplysia

Two neuroactive peptides, A and B, have been isolated from the atrial gland in the reproductive tract of Aplysia. Each of the two peptides is able to induce egg-laying behavior in recipient animals. In vitro recordings from the abdominal ganglion show that both peptides also trigger longlasting discharges in the bag cell neurons at concentrations around 0.1 muM. The peptides were purified by a combination of ammonium sulfate precipitation, agarose gel filtration, and cation exchange chromatography. Each peptide has 34 amino acid residues. Microsequencing together with carboxypeptidase Y degradation and analysis of tryptic peptides revealed the following sequence for peptide A: H-Ala-Val-Lys-Leu-Ser-Ser-Asp-Gly-Asn-Tyr-Pro-Phe-Asp-Leu-Ser-Lys-Glu-Asp-Gly -Ala-Gln-Pro-Tyr-Phe-Met-Thr-Pro-Arg-Leu-Arg-Phe-Tyr-Pro-Ile. Peptide B differs from A in only four positions. The first nine residues of B are: Ala-Val-Lys-Ser-Ser-Ser-Tyr-Glu-Lys-, whereas residues 10-34 of B are identical to those of A. The calculated M(r) of A is 3924 and that of B is 4032. The pI of peptide A as determined by isoelectric focusing in polyacrylamide gels is 7.9-8.1 and that of peptide B is 9.0-9.2. It is estimated that each atrial gland contains at least 150 mug of peptide A and 50 mug of B. Neither peptide resembles the egg-laying hormone isolated from bag cell neurons. It is postulated that the atrial gland peptides are released during copulation, and then by interacting with neuronal receptors in the head ganglia and pleuroabdominal connectives they cause the bag cells to afterdischarge, thereby releasing egg-laying hormone.

The degradation of human lung elastin by neutrophil proteinases

Human lung elastin has been isolated by both a degradative and nondegradative procedure and the products obtained found to have amino acid compositions comparable to published results. These elastin preparations, when utilized as substrates for various mammalian proteinases, were solubilized by porcine elastase at a rate six times faster than human leukocyte elastase. Leukocyte cathepsin G also solubilized lung elastin but only at 12% of the rate of the leukocyte elastase. In all cases the elastin prepared by nondegradative techniques proved to be the best substrate in these studies. The differences in the rate of digestion of elastin of the two elastolytic proteinases was readily attributed to the specificity differences of each enzyme as judged by carboxyterminal analysis of solubilized elastin peptides. The plasma proteinase inhibitors, alpha-1-proteinase inhibitor and alpha-2-macroglobulin abolished the elastolytic activity of both leukocyte enzymes, while alpha-1-antichymotrypsin specifically inactivated cathespsin G. Two synthetic inhibitors, Me-O-Suc-Ala-Ala-Pro-Val-CH2Cl (for elastase and Z-Gly-Leu-Phe-CH2Cl (for cathepsin G) were equally effective in abolishing the elastolytic activity of the two neutrophil enzymes. However, inhibition of leukocyte elastase by alpha-1-proteinase inhibitor was significantly suppressed if the enzyme was preincubated with elastin prior to addition of the inhibitor.