New fluorogenic substrates for alpha-thrombin, factor Xa, kallikreins, and urokinase

Twenty peptide-4-methylcoumarin amides (MCA) were newly synthesized and tested as possible substrates for alpha-thrombin, factor Xa, kallikreins, urokinase, and plasmin. These fluorogenic peptides contained arginine-MCA as the carboxyl-terminus. Release of 7-amino-4-methylcoumarin was determined fluorometrically. Of these peptides, the following were found to be specific substrates for individual enzymes: Boc-Val-Pro-Arg-MCA for alpha-thrombin, Boc-Ile-Glu-Gly-Arg-MCA, and Boc-Ser-Gly-Arg-MCA for factor Xa, Z-Phe-Arg-MCA for plasma kallikrein, Pro-Phe-Arg-MCA for pancreatic and urinary kallikreins, and glutaryl-Gly-Arg-MCA for urokinase. Moreover, these peptide-MCA substrates were resistant to plasmin.     

Separation and analysis of free ceramides containing 2-hydroxy fatty acids in Sphingobacterium species

Abstract The occurrence of free ceramides was shown in the chloroform-methanol extractable lipids of 16 strains of Sphingobacterium including three species: S. versatilis, S. multivorum and S. mizutae . The predominant long-chain base was identified as a branched-chain, saturated dihydroxy base with a carbon chain consisting of 17 carbon atoms, while the most abundant fatty acid was 2-hydroxy-13-methyltetradecanoic acid. The major molecular species of the intact ceramides were identified as LCB- d - iso -17 : 0-2-OH iso -15 : 0FA, LCB- d - iso -17 : 0- iso -15 : 0FA and LCB- d -n16 : 0- iso -15 : 0FA.     

Cloning and expression of cDNAs for the alpha subunit of the murine lymphocyte-Peyer''s patch adhesion molecule

cDNA clones encoding the alpha chain of the murine lymphocyte-Peyer's patch adhesion molecule (LPAM), which is associated with lymphocyte homing, have been isolated by screening with the human VLA-4 (alpha 4h) probe. Several alpha 4 antigenic determinants were identified on COS-7 cells after transfection. From overlapping clones, approximately 5 kb of contiguous nucleotide sequence have been determined, encoding a protein sequence of 1039 amino acids for the LPAM alpha chain (alpha 4m). LPAM is a member of the integrin family of cell-surface heterodimers, and alpha 4m is the murine homologue of the human alpha 4 h chain. The two proteins have a total sequence similarity of 84%, with an almost perfect conservation (31/32 amino acids) in the cytoplasmic domain. Like alpha 4h, alpha 4m is distinct from other integrin alpha chains because it has neither an I-domain nor a COOH-terminal cleavage site. The positions of the characteristic Cysteine residues are conserved, and a putative protease cleavage site is located near the middle of the protein sequence. The NH2-terminal part of the protein contains seven homologous repeats, and three of them include putative divalent cation-binding sites. These sites are among the most conserved between the alpha 4m sequence and other alpha chains, and may therefore be involved in the binding of integrin alpha and beta chains. An additional cDNA clone was isolated which shares a sequence of perfect homology with the alpha 4m encoding cDNAs, but has a unique 3' poly-A end. This observation correlates with the fact that three discrete murine RNA bands are observed in Northern blot experiments using alpha 4m as a probe, whereas only two human RNA species are described for alpha 4h, indicating a higher complexity for murine than for human sequences.     

Distribution, purification, and characterization of thermostable phenylalanine dehydrogenase from thermophilic actinomycetes.

Phenylalanine dehydrogenase (L-phenylalanine:NAD oxidoreductase, deaminating; EC 1.4.1.-) was found in various thermophilic actinomycetes. We purified the enzyme to homogeneity from Thermoactinomyces intermedius IFO 14230 by heat treatment and by Red Sepharose 4B, DEAE-Toyopearl, Sepharose CL-4B, and Sephadex G-100 chromatographies with a 13% yield. The relative molecular weight of the native enzyme was estimated to be about 270,000 by gel filtration. The enzyme consists of six subunits identical in molecular weight (41,000) and is highly thermostable: it is not inactivated by incubation at pH 7.2 and 70 degrees C for at least 60 min or in the range of pH 5 to 10.8 at 50 degrees C for 10 min. The enzyme preferably acts on L-phenylalanine and its 2-oxo analog, phenylpyruvate, in the presence of NAD and NADH, respectively. Initial velocity and product inhibition studies showed that the oxidative deamination proceeds through a sequential ordered binary-ternary mechanism. The Km values for L-phenylalanine, NAD, phenylpyruvate, NADH, and ammonia were 0.22, 0.078, 0.045, 0.025, and 106 mM, respectively. The pro-S hydrogen at C-4 of the dihydronicotinamide ring of NADH was exclusively transferred to the substrate.     

The 55-kilodalton protein in an oriC complex fraction is glycogen synthase.

Three proteins with molecular masses of 35, 55, and 75 kDa were found in an oriC complex fraction after purification through CsCl density gradient centrifugation (W. G. Hendrickson, T. Kusano, H. Yamaki, R. Balakrishnan, M. King, J. Murchie, and M. Schaechter, Cell 30:915-923, 1982). Of these three proteins, the 55-kDa protein was determined to be glycogen synthase on the basis of the N-terminal amino acid sequence and the molecular weight. The oriC complex was formed in glgA mutant cells, which produce no detectable glycogen, as well as in wild-type cells. None of the 35-, 55-, and 75-kDa proteins were detected in the fraction from this mutant. The results indicate that these proteins were not constituents of the oriC complex.     

Thyrotropin-secreting pituitary adenoma: a case report.

We report a 44-year-old male with a thyrotropin (TSH)-secreting pituitary adenoma. Based serum free triiodothyronine (FT3, 12.1 pmol/l) and free thyroxine (FT4, 28 pmol/l) were increased with normal basal TSH (3.1 mU/l). There was impaired TSH response to thyrotropin releasing hormone (TRH) test. Serum TSH was suppressed to 59% of the basal level after oral administration of 1.4 mg 3,3'-5-triiodothyroacetic acid (triac), whereas no suppression was observed after 75 micrograms daily administration of triiodothyronine (T3). Serum concentrations of alpha-subunit of TSH (TSH-alpha) and TSH-alpha/TSH molar ratio were high, being 1.95 micrograms/l, and 4.4, respectively. Pituitary CT and MRI scan showed the presence of a macroadenoma in the anterior lobe of the pituitary gland. Histopathology of the excised pituitary confirmed the diagnosis of a TSH-producing adenoma. A positive correlation between TSH and FT3 (r = 0.66, P less than 0.01) or FT4 (r = 0.54, P less than 0.01) was observed in serial sera obtained before and after operation.     

Tissue factor potentiates the factor VIIa-catalyzed hydrolysis of an ester substrate.

We designed a simple and sensitive method to assay the activity of the factor VIIa-tissue factor complex, using as a substrate N alpha-benzyloxycarbonyl-L-arginine p-nitrobenzyl ester (Z-Arg-ONb) (Zur, M., and Nemerson, Y. (1978) J. Biol. Chem. 253, 2203-2209). The principle was to measure the amount of p-nitrobenzyl alcohol released during ester hydrolysis using reversed-phase high performance liquid chromatography. Z-Arg-ONb had a broad specificity for plasma serine proteases and factor IXa. Using this method, we examined the effect of tissue factor on the esterase activity of factor VIIa under various conditions. We found that tissue factor greatly potentiates the factor VIIa-catalyzed hydrolysis of Z-Arg-ONb. Phospholipids were not required for the factor VIIa-catalyzed hydrolysis of Z-Arg-ONb, even in the presence of tissue factor. The Km value of factor VIIa alone toward the ester substrate was six times higher than that of a VIIa-tissue factor complex (3.2 versus 0.54 mM), whereas the kcat value was 12 times lower than that of the VIIa-tissue factor complex (14.3 versus 173 s-1). Thus, tissue factor apparently affects the catalytic site of factor VIIa and enhances hydrolysis of the ester substrate. This enhancing effect of tissue factor disappeared on removal of the gamma-carboxyglutamic acid domain from factor VIIa, whereas the esterase activity in the absence of tissue factor was not affected by this modification. The gamma-carboxyglutamic acid domain is probably required as a potent determinant for interactions with tissue factor, even in the absence of phospholipids in the reaction mixture.