Purothionin from wheat endosperm reversibly blocks myogenic differentiation of chick embryonic muscle cells in culture

Purothionin from wheat endosperm is a cysteine-rich, basic polypeptide of about 5000 Da, which modifies membrane permeability of cultured mammalian cells. This peptide was found to block fusion of chick embryonic muscle cells in culture but allows proliferation and alignment. A purothionin concentration of 6 micrograms/ml (1.2 microM) was necessary for the complete prevention of myotube formation. Under similar conditions, incorporation of [35S]methionine occurred normally but the synthesis of muscle-specific proteins including creatine kinase and acetylcholine receptor was strongly inhibited. In addition, purothionin blocked the uptake of 86Rb+, immediately after its addition to the cultured myoblasts. No such effects were found with the purothionin chemically modified with acetic or succinic anhydride. Thus, the basic residues in purothionin appear to be associated with the inhibition of myogenic differentiation. These results suggest that purothionin exerts its regulatory effect on the transition from proliferative to differentiative myoblasts by interfering with membrane permeability or intercellular contact and recognition, which are necessary for the initiation of muscle differentiation.

Na+, K+-specific inhibition of protein and peptide hydrolyses by proteasomes from human hepatoma tissues

Proteasomes were purified from human hepatoma tissues, and their sensitivities to Na+ and K+ were examined. At concentrations of 10 mM or more, these cations were found to inhibit completely polylysine-activated casein degradation by the purified proteasomes. They also strongly inhibited the hydrolyses of peptides, although to a lesser extent. On the other hand, they reversed the inhibitory and stimulatory effects of polylysine on the hydrolyses of Suc-Leu-Tyr-AMC and Cbz-Ala-Arg-Arg-MNA, respectively. These results suggest that Na+ and/or K+ may be involved in the regulation of intracellular protein breakdown by controlling the multicatalytic activity of proteasomes.

The use of lithium carbonate to correct leukopenia during cancer treatment

Leukopenia is a common complication noted in patients receiving radiotherapy and/or chemotherapy but no effective method has been reported so far to correct this complication. In the field of psychiatry, lithium carbonate used in treating depression has been noted to have induced leukocytosis as a side effect. From July 1985 to December 1987, a total of 111 patients receiving radiotherapy and/or chemotherapy with leukopenia were included in this study. There were sixty nine patients who received lithium carbonate and the remaining forty two patients served as control group were allowed to stop their primary treatment temporarily without medication during their period of leukopenia. For the group given lithium carbonate, 79% of the patients were able to recover their white blood count (WBC) above 3,000/cu.mm. within 5 days and finished their primary treatment smoothly. For the control group, it took them on the average about 11.8 days of rest in order to recover their WBC level to 3,000/cu.mm. and above. Reports in the recent literature indicates that the average toxic level is around 1.5 mEq/l to 2.0 mEq/l. In our study, the average serum lithium level before administration is 0.44 mEq/l, it reached 0.59 mEq/l and 1.08 mEq/l after the fifth and the 10th day of intake respectively. From this laboratory data, obviously no patient reached the toxic level and no side effects were noted clinically. Based on these figures, we can see clearly that lithium carbonate can shorten the period of leukopenia in comparison to the control group which was not given any medication.

Adjuvant PSK immunotherapy in patients with carcinoma of the nasopharynx

A controlled study using adjuvant PSK immunotherapy in patients with nasopharyngeal carcinoma was initiated with the aim of improving survival by enhancing the host immune system against tumour cells. A total of 38 patients were randomly selected, all of whom had previously received radiotherapy with or without chemotherapy. Eight patients in the PSK immunotherapy group (n = 21) developed local recurrence, three of whom later died due to distant metastasis. In the control group (n = 17) three patients developed local recurrence while six patients developed distant metastasis. All of these six patients later died due to disease progression. It seems that PSK exerts its antitumour effect systemically; the risk of distant metastasis occurring is decreased, but it is apparently ineffective in improving local disease control. The estimated median survival time of the PSK-treated group compared with the control was significantly increased (35 months versus 25 months, P = 0.043). The 5-year survival rate was also significantly better in the PSK immunotherapy group (28% versus 15%, P = 0.043). It is concluded that PSK deserves careful consideration as an important immunotherapeutic agent in the management of nasopharyngeal carcinoma.

Protease Ti from Escherichia coli requires ATP hydrolysis for protein breakdown but not for hydrolysis of small peptides

Protease Ti, a new ATP-dependent protease in Escherichia coli, degrades proteins and ATP in a linked process, but these two hydrolytic functions are catalyzed by distinct components of the enzyme. To clarify the enzyme's specificity and the role of ATP, a variety of fluorogenic peptides were tested as possible substrates for protease Ti or its two components. Protease Ti rapidly hydrolyzed N-succinyl(Suc)-Leu-Tyr-amidomethylcoumarin (AMC) (Km = 1.3 mM) which is not degraded by protease La, the other ATP-dependent protease in E. coli. Protease Ti also hydrolyzed, but slowly, Suc-Ala-Ala-Phe-AMC and Suc-Leu-Leu-Val-Tyr-AMC. However, it showed little or no activity against basic or other hydrophobic peptides, including ones degraded rapidly by protease La. Component P, which contains the serine-active site, by itself rapidly degrades the same peptides as the intact enzyme. Addition of component A, which contains the ATP-hydrolyzing site and is necessary for protein degradation, had little or no effect on peptide hydrolysis. N-Ethylmaleimide, which inactivates the ATPase, did not inhibit peptide hydrolysis. In addition, this peptide did not stimulate the ATPase activity of component A (unlike protein substrates). Thus, although the serine-active site on component P is unable to degrade proteins, it is fully functional against small peptides in the absence of ATP. At high concentrations, Suc-Leu-Tyr-AMC caused a complete inhibition of casein breakdown, and diisopropylfluorophosphate blocked similarly the hydrolysis of both protein and peptide substrates. Thus, both substrates seem to be hydrolyzed at the same active site on component P, and ATP hydrolysis by component A either unmasks or enlarges this proteolytic site such that large proteins can gain access to it.

Amino acid sequence of a probable amylase/protease inhibitor from rice seeds

The primary structure of a 9-kDa basic protein from rice seeds was determined by gas-phase sequencing of the intact protein and peptides derived from it by digestion with trypsin, chymotrypsin, and endopeptidase Lys-K. The protein consists of a single polypeptide chain of 91 amino acid residues with a calculated molecular mass of 8909 Da. It is rich in alanine, serine, glycine, and cysteine. The eight cysteines form four disulfide bonds. There is no methionine, histidine, phenylalanine, or tryptophan. The sequence is highly homologous with an alpha-amylase inhibitor, I-2, from seeds of Indian finger millet [F. A. P. Campos and M. Richardson (1984) FEBS Lett. 167, 221-225] and a 10-kDa barley seed protein, also called a probable amylase/protease inhibitor [B. Svensson et al. (1986) Carlsberg Res. Commun. 51, 493-500; J. Mundy and J. C. Rogers (1986) Planta 169, 51-63]. In analogy with the barley protein, the purified protein is tentatively called a rice probable amylase/protease inhibitor (PAPI). The rice PAPI does not show inhibitory activities against proteases and amylases tested. The amino acid sequence is as follows: Ile-Thr-Cys-Gly-Gln-Val-Asn-Ser-Ala-Val(10)-Gly-Pro-Cys-Leu-Thr-Tyr- Ala-Arg-Gly-Gly(20)-Ala-Gly-Pro-Ser-Ala-Ala-Cys-Cys-Ser-Gly(30)-Val-Arg- Ser-Leu-Lys-Ala-Ala-Ala-Ser-Thr(40)-Thr-Ala-Asp-Arg-Arg-Thr-Ala-Cys- Asn-Cys(50)-Leu-Lys-Asn-Ala-Ala-Arg-Gly-Ile-Lys-Gly(60)-Leu-Asn-Ala-Gly- Asn-Ala-Ala-Ser-Ile-Pro(70)-Ser-Lys-Cys-Gly-Val-Ser-Val-Pro-Tyr-Thr(80)- Ile-Ser-Ala-Ser-Ile-Asp-Cys-Ser-Arg-Val-Ser(91).

Protease Ti, a new ATP-dependent protease in Escherichia coli, contains protein-activated ATPase and proteolytic functions in distinct subunits

In addition to protease La (the lon gene product), Escherichia coli contains another ATP-dependent protease, Ti. This enzyme (approximately 340 kDa) is composed of two components, both of which are required for proteolysis. Both have been purified to homogeneity by conventional procedures using [3H]casein as the substrate. The ATP-stabilized component, A, has a subunit molecular weight of 80,000 upon gel electrophoresis in the presence of sodium dodecyl sulfate, but it behaves as a dimer (140 kDa) upon gel filtration. Component P, which is relatively heat stable, is inactivated by diisopropyl fluorophosphate and can be labeled with [3H] diisopropyl fluorophosphate. It has a subunit size of 23 kDa, but the isolated component behaves as a complex (260 kDa) of 10-12 subunits. The isoelectric point of component A is 7.0 and that of P is 8.2, and their amino acid compositions differ considerably. The purified enzyme has an ATPase activity that is stimulated 2-4-fold by casein and other protein substrates but not by nonhydrolyzed proteins. Component A also shows ATPase activity which can be stimulated by casein. Addition of component P (which lacks ATPase activity) inhibits basal ATP hydrolysis by A and makes this ATPase more responsive to casein. Although component P contains the serine active site for proteolysis, it shows no proteolytic activity in the absence of component A, Mg2+, and ATP or dATP. Other nucleoside triphosphates are not hydrolyzed and do not support proteolysis. Protease Ti has a Km for ATP of 210 microM for hydrolysis of both casein and ATP. Casein increases the Vmax for ATP without affecting the Km. A Mg2+ concentration of 5 mM is necessary for half-maximal rates of ATP and casein hydrolysis. Ca2+ and Mn2+ partially support these activities. Thus, protease Ti shares many unusual properties with protease La (e.g. coupled ATP and protein hydrolysis and protein-activated ATPase), but these functions in protease Ti are associated with distinct subunits that modify each other's activities.

Protease So from Escherichia coli preferentially degrades oxidatively damaged glutamine synthetase

After oxidative damage (e.g. induced with iron, ascorbate, and oxygen), the inactivated glutamine synthetase is selectively hydrolyzed in extracts of Escherichia coli. We therefore tested if glutamine synthetase treated with this system is hydrolyzed preferentially by any of the known E. coli proteases. Protease So, a cytoplasmic serine protease, was found to degrade the oxidized form of glutamine synthetase to acid-soluble peptides 5-10 times faster than the native glutamine synthetase. Degradation of the oxidized glutamine synthetase was inhibited by EDTA and stimulated 5-10-fold by Mg2+, Ca2+, or Mn2+, even though casein hydrolysis by protease So is not affected by divalent cations. Apparently, these cations affect the conformation of this substrate, making it more susceptible to proteolytic attack. Protease Re, another cytoplasmic protease, also degrades preferentially the oxidized form of glutamine synthetase and seems to correspond to the glutamine synthetase-degrading activity recently described by Roseman and Levine [1987) J. Biol. Chem. 262, 2101-2110). However, it is much less active in this reaction than protease So. No other soluble E. coli protease, including Do, Ci, Mi, Fa, Pi, or the ATP-dependent proteases Ti and La (the lon product), appears to degrade this oxidized protein. These results suggest that protease So participates in the hydrolysis of oxidatively damaged proteins and that E. coli has multiple systems for degrading different types of aberrant proteins.

Dose dependent effect of cimetidine on procainamide disposition in man

This study investigated the influence of single dose of 200 mg and 400 mg cimetidine on the pharmacokinetics of procainamide (PA) in healthy Chinese. The results show that AUC of PA was significantly raised by 38% and 24% with a significant reduction in renal clearance by 40% and 31%, respectively, when single dose of 400 mg or 200 mg cimetidine was coadministered. Significant changes of AUC and renal clearance of the active metabolite--N-acetylprocainamide (NAPA) were found only following the dose of 400 mg cimetidine. The larger dose of cimetidine produced greater alteration in the PA and NAPA pharmacokinetics. The interaction is mainly associated with their reduced renal clearance.

Purification and characterization of protease Re, a cytoplasmic endoprotease in Escherichia coli

Protease Re, a new cytoplasmic endoprotease in Escherichia coli, was purified to homogeneity by conventional procedures, using [3H]casein as the substrate. The enzyme consists of a single polypeptide of 82,000 molecular weight. It is maximally active between pH 7 and 8.5 and is independent of ATP. It has a pI of 6.8 and a Km of 10.8 microM for casein. Since diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride inhibited this enzyme, it appears to be a serine protease. Protease Re was sensitive to inhibition by L-1-tosylamido-2-phenylethylchloromethylketone but not to that by 1-chloro-3-tosylamido-7-aminoheptanone, thiol-blocking reagents, chelating agents, or various peptide aldehydes. Re also degraded [125I]globin, [125I]glucagon, and 125I-labeled denatured bovine serum albumin to acid-soluble products (generally oligopeptides of greater than 1,500 daltons), but it showed no activity against serum albumin, growth hormone, insulin, or a variety of fluorometric peptide substrates. It also hydrolyzed oxidatively inactivated glutamine synthetase (generated by ascorbate, oxygen, and iron) four- to fivefold more rapidly than the native protein. Protease Re appears to be identical to the proteolytic enzyme isolated by Roseman and Levine (J. Biol. Chem. 262:2101-2110, 1987) by its ability to degrade selectively oxidatively damaged glutamine synthetase in vivo. Its role in intracellular protein breakdown is uncertain.

Escherichia coli contains a soluble ATP-dependent protease (Ti) distinct from protease La

The energy requirement for protein breakdown in Escherichia coli has generally been attributed to the ATP-dependence of protease La, the lon gene product. We have partially purified another ATP-dependent protease from lon-cells that lack protease La (as shown by immunoblotting). This enzyme hydrolyzes [3H]methyl-casein to acid-soluble products in the presence of ATP and Mg2+. ATP hydrolysis appears necessary for proteolytic activity. Since this enzyme is inhibited by diisopropyl fluorophosphate, it appears to be a serine protease, but it also contains essential thiol residues. We propose to name this enzyme protease Ti. It differs from protease La in nucleotide specificity, inhibitor sensitivity, and subunit composition. On gel filtration, protease Ti has an apparent molecular weight of 370,000. It can be fractionated by phosphocellulose chromatography or by DEAE chromatography into two components with apparent molecular weights of 260,000 and 140,000. When separated, they do not show proteolytic activity. One of these components, by itself, has ATPase activity and is labile in the absence of ATP. The other contains the diisopropyl fluorophosphate-sensitive proteolytic site. These results and the similar findings of Katayama-Fujimura et al. [Katayama-Fujimura, Y., Gottesman, S. & Maurizi, M. R. (1987) J. Biol. Chem. 262, 4477-4485] indicate that E. coli contains two ATP-hydrolyzing proteases, which differ in many biochemical features and probably in their physiological roles.

PSK immunotherapy in cancer patients--a preliminary report

A clinical trial was conducted by the Department of Radiation Oncology, Mackay Memorial Hospital, between 1981 and 1986, using PSK (Krestin) as an adjuvant immunotherapy to assess its potential benefit in cancer patients. The protocol called for a daily administration of 1 gram tid of PSK orally for at least a month upon completion of primary treatment for the tumor. A total of 67 patients were included in this study; 13 patients were excluded from evaluation because of noncompliance with the protocol. When three cases of toxicity were noted, PSK was discontinued for the three patients. Among the different groups of patients, nasopharyngeal carcinoma patients under PSK immunotherapy showed a significantly better survival when compared with historical controls (28% vs 17% five-year survival rate, p less than 0.05, generalized Wilcoxon test). It is therefore concluded that PSK can serve as an important adjunct in the treatment of nasopharyngeal carcinoma.

Subepidermal capillary basement membrane thickness of the skin obtained by punch biopsy in patients with non insulin dependent diabetes mellitus

Thickening and proliferation of the capillary basement membrane is a generalized phenomenon in diabetes mellitus and has been described in many organs including the heart, kidney, pancreas, retina etc. While such changes are specific, it is difficult to obtain specimens from those organs. Tissue samples were obtained from the medial surface of the thigh of 33 diabetics and 4 healthy controls by means of punch biopsy. Measurements carried out by normogram obtained from electron microscopic pictures. HbA1c values were also determined at time of muscle biopsy. 1. The HbA1c values are higher in diabetics than in the control group (p<0.01). 2. The subepidermal capillary basement membrane thickness of the diabetics: 30% of the 5’th decade population, 53.9% of the 6’th decade population and 83.3% of the 7’th decade population was greater than 3,000 A°. Whereas that of the controls was less than 3,000 A°. 3. The subepidermal capillary basement membrane thickness was not significantly increased with the duration of the disease. 4. In cases of greater subepidermal capillary besement membrane thickness, HbA1c showed a significant increase. (p<0.01).

ent-Kaurene Biosynthesis in Cell-Free Extracts of Excised Parts of Tall and Dwarf Pea Seedlings

Investigations on the sites of ent-kaur-16-ene (ent-kaurene) biosynthesis were conducted with cell-free extracts from several excised parts of 10-, 13-, and 16-d-old tall and dwarf pea (Pisum sativum L.) seedlings. [(14)C]Mevalonic acid was incorporated into ent-kaurene in cell-free extracts from young developing leaves and elongating internodes of tall (;Alaska') and dwarf (;Progress No.9') pea seedlings at all three stages of development. ent-Kaurene biosynthesis also occurred readily in cell-free extracts from shoot tips, petioles, and stipules near the young elongating internodes. The ent-kaurene-synthesizing activity found in young developing tissues declined as tissues matured. Little or no activity was detectable in enzyme extracts from cotyledons and root tips at different stages. In light grown tall pea internodes ent-kaurene-synthesizing activity was low as they began to elongate, reached a maximum when the internodes reached about 2 cm in length and declined as they matured. Activity in extracts of dwarf shoot tips and internodes was generally lower than in equivalent tall plants, but the activity in dwarf leaves and stipules was somewhat higher than in tall plants. With the exception of root tips, there is a strong correlation between growth potential of a tissue and the rate of ent-kaurene biosynthesis in extracts from that tissue.

Serum and erythrocyte lipoperoxides and supproxide dismutase levels in normal persons and hypertensive patients

To assess the role and responses of lipoperoxide and superoxide dismutase in hypertensive disease, the serum and erythrocyte lipid peroxide and erythrocyte superoxide dismutase levels were measured in 65 normal persons and hypertensive patients.

The results are summerized as follows: In normal persons, serum and erythrocyte lipoperoxide values showed an increase according to age, but the elevation was not statistically significant. In normal persons, the erythrocyte superoxide dismutase value did not change according to age. In hypertensive patients, the serum and erythrocyte lipoperoxide values showed increases of 10.8% and 26% respectively compared to those of the controls. In hypertensive patients, the erythrocyte superoxide dismutase value showed a decrease of 29.9% compared to that of the controls.

Purification from Escherichia coli of a periplasmic protein that is a potent inhibitor of pancreatic proteases

A protein capable of inhibiting trypsin and other pancreatic proteases has been purified to homogeneity from Escherichia coli by conventional procedures and affinity chromatography. It is stable for at least 30 min at 100 degrees C and pH 1.0, but it is inactivated by digestion with pepsin. The inhibitor has an apparent molecular weight of 38,000 as determined by gel filtration and must be a homodimer since it contains a single 18,000-dalton subunit upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The inhibitor has an isoelectric point of 6.1. One dimeric molecule of the inhibitor can bind two trypsin molecules to form a mixed tetrameric complex, in which trypsin molecules are completely inhibited. The inhibitor is not digested by the trypsin. When N-benzoyl-DL-arginine-p-nitroanilide was used as a trypsin substrate, half-maximal inhibition was observed at 22 nM. This protein also inhibits chymotrypsin, pancreatic elastase, rat mast cell chymase, and human serosal urokinase, but it does not inhibit human pulmonary tryptase, kallikrein, papain, pepsin, Staphylococcus aureus V8 protease, subtilisin, and thermolysin. Surprisingly, it did not inhibit any of the eight soluble endoproteases recently isolated from E. coli (i.e. proteases Do, Re, Mi, Fa, So, La, Ci, and Pi) nor the chymotrypsin-like (protease I) and trypsin-like (protease II) esterases in E. coli. The inhibitor is localized to the periplasmic space and its level did not change with different growth media or stages of cell growth. The physiological function of this E. coli trypsin inhibitor is unknown. We suggest that E. coli trypsin inhibitor be named "Ecotin."