C-Terminal peptidyl-L-proline hydrolase activity of Aspergillus acid carboxypeptidase.

Aspergillus saitoi acid carboxypeptidase hydrolyzed C-terminal peptidyl-L-proline bonds and released the C-terminal proline from Z-Gly-Pro-Leu-Gly-Pro and Z-Gly-Pro at pH 3.3. Proline liberated by the enzymic reaction was measured by a sensitive colorimetric ninhydrin method in glacial acetic acid at 513 nm. A Km value of 1.0 mM and a kcat value of 0.09 s-1 for Z-Gly-Pro-Leu-Gly-Pro hydrolysis, and a Km value of 5.0 mM and a kcat value of 0.0045 s-1 for Z-Gly-Pro hydrolysis were calculated from Lineweaver-Burk plots.     

Synthetic ColE1 plasmids carrying genes for penicillin-binding proteins in Escherichia coli

Clarke and Carbon's collection of 2000 Escherichia coli strains which harbor ColE1 plasmids carrying small random segments of the E. coli chromosome was screened for the correction of mutational defects in penicillin-binding proteins (PBPs): ponA (PBP-1a), ponB (PBP-1b), dacB (PBP-4), and pfv (PBP-5). We found plasmids carrying chromosomal segments containing ponA⁺-aroB⁺ (pLC29-47), ponB⁺-tonA⁺ (pLC4-43, pLC4-44, and pLC19-19), and argG⁺-dacB⁺ (pLC10-46 and pLC18-38). Characters of these plasmids were analyzed. Two other plasmids (pLC26-6 and pLC4-14) previously found to correct ftsI mutation (Y. Nishimura, Y. Takeda, A. Nishimura, H. Suzuki, M. Inouye, and Y. Hirota (1977)Plasmid1, 67–77) were also investigated further. Restriction maps of chromosomal DNAs carried by pLC29-47, pLC4-44, pLC19-19, pLC18-38, pLC26-6, and pLC4-14 were constructed. The regions of ponB-tonA on pLC4-44 and pLC19-19, and of leuA-ftsI-murE and F on pLC26-6 were located on the restriction maps. Although both pLC26-6 and pLC4-14 corrected a thermosensitive mutation, ftsI, which causes a defect in cell division due to abnormal PBP-3, only pLC26-6 led to restoration of PBP-3 production by an ftsI mutant, while pLC4-14 did not. Restriction and heteroduplex analyses of pLC26-6 and pLC4-14 have shown the absence of nucleotide sequence homology between them. The plasmids, pLC29-47 carrying ponA⁺ and pLC4-43, pLC4-44, and pLC19-19 carrying ponB⁺ led the host cell to overproduce the respective PBP.     

Anti-pituitary antibodies in patients with hypopituitarism and their families: longitudinal observation.

In an attempt to investigate the clinical significance of anti-pituitary antibodies in patients with hypopituitarism, anti-pituitary antibody in plasma was examined in 10 such patients (7 cases of isolated ACTH deficiency, 1 of partial hypopituitarism, and 2 of Sheehan's syndrome), on two or three occasions with an interval of more than 6 months (longitudinal study). In a total of 16 relatives of these 4 patients (2 cases of Sheehan's syndrome, one in each of partial hypopituitarism and isolated ACTH deficiency) and one patient not involved in the longitudinal study, anti-pituitary antibodies were also examined (family study). Anti-pituitary antibodies reacting with rat pituitary cytoplasmic antigens (pituitary cell antibodies: PCA) and pituitary cell surface antibodies (PCSA) reacting with GH3 cells and/or AtT-20 cells were measured with indirect immunofluorescence. The longitudinal study revealed the disappearance of antibodies in 3 patients, 2 PCA positive and one both PCA and PCSA positive. In 3 patients, altered antibody titers or a newly appearing antibody were found during the follow-up period. In 4 patients, the pituitary antibodies were negative during the follow-up periods. Of 16 family members studied, positive PCA was found in 3 members (2 in the families of patients with PCA positive Sheehan's syndrome, and 1 in the family of the patients with PCA positive partial hypopituitarism). Positive PCSA was found in 4 members (one in each of families of patients with partial hypopituitarism and isolated ACTH deficiency and of two cases of Sheehan's syndrome), and weakly positive PCSA was found in one family member of a patients with PCA positive Sheehan's syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protein kinase C in rat brain synaptosomes. Beta II-subspecies as a major isoform associated with membrane-skeleton elements.

A small fraction (approximately 5%) of protein kinase C (PKC) in the adult rat brain synaptosomes is tightly associated with Triton X-100-insoluble components (most likely membrane-skeleton elements), and is solubilized only after denaturation with sodium dodecyl sulfate. The kinase domain of this PKC can be released as a soluble form after limited proteolysis with calpain, whereas the regulatory domain which binds phorbol ester remains insoluble. The PKC in this fraction was identified as the beta II-subspecies or its related molecule. Presumably, this enzyme subspecies is responsible for the phosphorylation of a major PKC substrate protein, growth-associated protein-43, which is located in nerve endings as well as in growth cones in association with the membrane-skeleton elements.     

Secretory regulation of 19-hydroxyandrostenedione in normal man.

To evaluate the secretory regulation of 19-hydroxyandrostenedione (19-OH-AD), its plasma concentration was measured before and after stimulation and inhibition tests for the ACTH-adrenal axis and the renin-angiotensin system in 50 normal subjects. Basal levels of plasma 19-OH-AD did not correlate with either those of plasma renin activity (PRA) or the plasma aldosterone concentration (PAC), but positively correlated with those of plasma cortisol. Plasma 19-OH-AD was stimulated by 0.25 mg ACTH-(1-24) and was suppressed by 1 mg dexamethasone (DEX) as were plasma cortisol and PAC. On the other hand, with 2-h standing alone or iv 40 mg furosemide plus 2-h standing, plasma 19-OH-AD and cortisol did not increase but PRA and PAC did. With iv furosemide plus 2-h standing with 3 mg DEX pretreatment, plasma 19-OH-AD and cortisol did not respond either, but PRA and PAC increased. With 25 mg oral captopril following 1-h standing with 3 mg DEX pretreatment, plasma 19-OH-AD and cortisol did not change but PAC decreased. These results indicate that the secretion of 19-OH-AD is mainly under the control of the ACTH-adrenal axis rather than the renin-angiotensin system.     

The effect of alpha-tocopherol as an antioxidant on the oxidation of membrane protein thiols induced by free radicals generated in different sites

Azo compounds enable us to generate peroxyl radicals by thermal decomposition at a constant rate and at a desired site, that is, water-soluble compounds produce initiating radicals in an aqueous phase and lipid-soluble compounds initiate the oxidation within the membrane-lipid layer. Using these radicals generated in different sites, we oxidized red blood cell ghost membranes to study the relationships between alpha-tocopherol depletion, initiation of lipid peroxidation, and protein damage. When radicals were generated in the aqueous phase, the loss of membrane protein thiols was observed concurrently with the consumption of membrane tocopherol and after tocopherol was exhausted the peroxidation of membrane lipids occurred. On the other hand, when radicals were initiated within the lipid region, the oxidation of thiols and the formation of thiobarbituric acid-reactive substances were suppressed to give an induction period until tocopherol fell below a critical level. Our results indicate that the surface thiols of extrinsic proteins may compete with alpha-tocopherol for trapping aqueous radicals and spare tocopherol to some extent, whereas the oxidation of intrinsic buried thiols may commence due to lipid-derived radicals produced after tocopherol was consumed. In conclusion, alpha-tocopherol in the membrane can break the free radical chain efficiently to inhibit the lipid peroxidation. However, the effect of tocopherol on the inhibition of membrane protein damage, exhibited by the loss of thiols and the formation of high-molecular-weight proteins, would be different depending on the site of initial radical generation.     

Microtubule destabilization by cdc2/H1 histone kinase: phosphorylation of a "pro-rich region" in the microtubule-binding domain of MAP-4.

Microtubule-associated protein-4 (MAP-4), a major MAP in proliferating cells, consists of a microtubule-binding domain and a projection domain protruding from the microtubule wall. The former contains a Pro-rich region and an assembly-promoting (AP) sequence region which is common to the neuron-specific MAPs, MAP-2 and tau1. In this paper, we describe the phosphorylation of the Pro-rich region of MAP-4 and the suppression of its assembly-promoting activity by cdc2/H1 histone kinase. This inactivation of MAP-4 may cause disassembly of the interphase microtubular network at the end of the G2 phase of the cell cycle.     

Identity of a tumor cytotoxic factor from human fibroblasts and hepatocyte growth factor

Human embryonic lung diploid fibroblast, IMR-90 cells secreted a tumor cytotoxic factor. The fibroblast-derived tumor cytotoxic factor (F-TCF) has a cytotoxic activity to Sarcoma 180 and a cytostatic and degenerative activities to KB cells. F-TCF has been purified about 540,000-fold with 23.3% recovery from 75 liters of the conditioned medium containing 5% newborn calf serum. The purified F-TCF is a basic glycoprotein with isoelectric point values of 7.4 to 8.6. It was stable in the pH range from 6.0 to 9.0 and was stable at the heating temperature of 60 degrees C for 10 min, but completely inactivated by reducing it with 2-mercaptoethanol. F-TCF has molecular weight of 76 to 80 kD on SDS-PAGE under non-reducing conditions and is a heterodimer consisting of a large alpha subunit with 52 to 56 kD and a small beta subunit with 30 to 34 kD. F-TCF was identified as one of human hepatocyte growth factors by the physicochemical properties including N terminal and a few internal amino acid sequences. We have confirmed that F-TCF has an ability to dramatically stimulate DNA synthesis in adult rat hepatocytes in the low dose range of 1 to 10 ng/ml.     

Effect of streptokinase on prostacyclin synthesis and phospholipase activity in cultured pulmonary artery endothelial cells

In this study, we examined the effects of streptokinase on arachidonic acid release and prostacyclin biosynthesis in cultured bovine pulmonary artery endothelial cells. When intact cells were incubated with streptokinase, a significant stimulatory effect on prostacyclin biosynthetic activity in cells was evident without any cellular damage at all concentrations used (1-10,000 units/ml). Streptokinase also caused a marked release of arachidonic acid. It induced rapid phospholipid hydrolysis, resulting in the release of up to 15% of incorporated [3H]arachidonic acid into the medium. After the addition of streptokinase, degradation of phosphatidylcholine and phosphatidylethanolamine was observed and lysophosphatidylcholine and lysophosphatidylethanolamine were produced. We also observed a transient rise in diacylglycerol after the addition of streptokinase. To test for phospholipase C activity, the release of incorporated [3H]choline, [3H]inositol and [3H]ethanolamine into the culture medium was determined. The level of radioactive inositol showed an increase, but the changes in choline and ethanolamine were comparatively small. An increase in inositol was detectable within 1 min after streptokinase addition and peaked after 15 min. Inositol phosphate and inositol trisphosphate were released, and these releases were suppressed by the addition of neomycin (50 microM). These results suggest that streptokinase stimulates phospholipase A2 and C activity, and that prostacyclin biosynthesis is subsequently increased in cultured endothelial cells.