Purification and properties of N-formylmethionine aminopeptidase from rat liver

A specific enzyme for the liberation of N-terminal N-formylmethionine from N-formylmethionyl peptides was purified 4750-fold from rat liver by successive applications of (NH4)SO4 precipitation, DEAE-cellulose, N-formylbestatin-AH-Sepharose 4B and AH-Sepharose 4B chromatography followed by Sepharose CL-6B gel filtration. The molecular weight was determined by gel filtration on Sepharose CL-6B as 290 000 +/- 5000. This was suggested to be a tetramer consisting of a subunit which was shown by sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis to have a 72 000 +/- 2000 molecular weight. The optimum pH of the enzyme was 7.8. Cd2+ and Hg2+ were highly toxic to the enzyme. Michaelis constants of N-formylmethionyl leucine and N-formylmethionine beta-naphthylamide were 0.03 and 0.2 mM, respectively.

Antianaphylactic effects of dipivalyl epinephrine and related compounds in rat conjunctiva

Topically applied dipivalyl epinephrine (DPE) and related compounds have been found to inhibit passive anaphylactic reaction in rat conjunctiva. The order of activity is as follows: isoproterenol greater than DPE greater than epinephrine greater than norepinephrine. The antianaphylactic effect of DPE was antagonized by propranolol but was not affected by phentolamine. The effects of epinephrine, norepinephrine, and isoproterenol were also antagonized by propranolol but potentiated by pentolamine. From these findings, it was suggested that DPE not only exerts its antianaphylactic action through activation of beta-adrenergic receptor but also itself has a little different action from epinephrine.

Antitumor anthracycline antibiotics, aclacinomycin A and analogues. I. Taxonomy, production, isolation and physicochemical properties

Aclacinomycin A and B, two major components of a new antitumor antibiotic complex, and their 19 analogues were produced by a culture of strain No. MA144-M1, which was identified as Streptomyces galilaeus. They were isolated by chelation with copper ion and silicic acid chromatography, and characterized by physicochemical methods in the anthracycline group of antibiotics.

Potentiative effects of sulfhydryl compounds on carrageenin-induced oedema in rats and relationship to their potencies as inhibitors of angiostin-coverting enzyme in vivo

Carrageenin-induced oedema in rats was potentiated by oral administration of (4R)-3-[(2S)-3-mercapto-2-methylpropanoyl]-4-thiazolidinecarboxylic acid (SA291) and related sulfhydryl compounds, and the effect was closely correlated with their potencies as inhibitors of angiotensin-converting enzyme in vivo.

Anodal electrotonus using a separate electrode to suppress pain during cavity preparation in labiocervical cavities

A method to apply anodal electrotonus during the cavity preparation in labiocervical cavities was presented. The amount of the electrotonus through a separate different electrode was determined to the maximum allowable current which ranged between 0.1 and 1.5 mA. In 35 teeth from 22 patients, analgesia, starting from the introduction of anodal tonus to the end of the cavity preparation, was observed in 22 (63%) teeth.

The effect of formycin on the processing of transfer RNA precursors in the posterior silk gland of Bombyx mori

Formycin, an adenosine analog, was used in studies of RNA synthesis by silk glands of silkworms in organ culture. Formycin has been shown to inhibit preferentially the incorporation of [3H]uridine into low molecular weight RNA in the cytoplasm. When silk glands were pulse-chase labeled with [3H]uridine in the presence of formycin, the synthesis of 4.5S tRNA precursors was not affected, as determined by gel electrophoresis. However, the accumulation of mature 4S tRNA was greatly reduced in the formycin-treated system, although the precursors synthesized disappeared from the 4.5S region on chase at the same rate as in the control system. [14C]Formycin was incorporated into the 4.5S precursors but not into 4S tRNA. These findings suggest that the inhibition of tRNA synthesis by formycin is due to the existence of some degradation mechanisms of formycin-containing 4.5S precursor RNA's and the failure to process them into normal 4S tRNA.

Synthesis and structure-activity relationships of bestatin analogues, inhibitors of aminopeptidase B

Stereoisomers and analogues of bestatin, [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]-L-leucine, were synthesized and tested for aminopeptidase B and leucine aminopeptidase inhibiting activity. Among the eight stereoisomers, the 2S stereoisomers exhibited strong activity. In a series of compounds in which the L-leucine residue of bestatin was substituted with other amino acids, only the one containing isoleucine showed more activity than bestatin. Norleucine, norvaline, methionine, valine, serine, glutamine, phenylalanine, glutamic acid, proline, and lysine analogues gave, in that order, decreasing activity. Alkyl and phenyl sub stitution for the benzyl group of bestatin decreased the activity markedly. p-Methyl-, p-chloro-, and p-nitrobestatins showed greater activity than bestatin.

Aminopeptidase activities on the surface of mammalian cells

Activities of hydrolytic enzymes on the surface of monkey kidney, canine kidney, L. FM3A and various tumor cells were determined and compared with those in the cell homogenate. Although aminopeptidase (EC 3.4.11.-) activities were always detected on the surface membrane in mammalian cells, trypsin, chymotrypsin and elastase activities were not detected while slight glycosidase activity was detected in a suspension of cultured cells. The activities of alanine-, leucine-, methionine- and phenylalanine-aminopeptidases were rather high but aminopeptidase A, proline-, valine-, glycyl propline dipeptidyl-and glycyl propyl leucine-tripeptidyl-aminopeptidases showed relatively low activities. Aminopeptidase activity was also demonstrated in the isolated membrane fractions. The specific activities of enzymes in these membrane fractions were not significantly greater than in cell homogenate so it was concluded that these enzyme activities were rather loosely bound to the cell membrane. Further evidence for the localization of the aminopeptidase activities on the cell surface was obtained by using glass-bead-bound substrate and detecting the release of the terminal residues. When bestatin, a specific inhibitor against aminopeptidase B and leucine aminopeptidase, was included in the assay system for the enzyme activities on the cell surface, the enzymes were commonly inhibited in all types of cells.