5-Oxoprolinase from rat kidney, I. Assay, purification, and determination of kinetic parameters.

A new assay for the determination of 5-oxoprolinase activity is described. The enzyme 5-oxoprolinase was purified from rat kidney 285-fold to apparent homogeneity, as judged by analytical disc electrophoresis and discontinous polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate. The specific activity of the preparation was 122 mU/mg of protein. A complete initial rate kinetic analysis of the forward reaction catalyzed by 5-oxoprolinase was carried out using 5-oxo-L-proline and MgATP2theta as substrates. The computer-fitted double reciprocal plots showed intersecting patterns indicating a sequential mechanism. The data were fitted by weighted linear regression analysis using the complete equation for bisubstrate reactions. The limiting Michaelis constants for 5-oxoproline and MgATP2theta were calculated to be 31.6 +/- 2.3 muM and 172.7 +/- 11.5muM, respectively. The maximum forward rate is 1.2 +/- 0.02 mumol X min-1; the turnover number 7.0 min-1.     

An adenosine 3':5' monophosphate dependent protein kinase from sea urchin spermatozoa.

A cyclic AMP dependent protein kinase (EC 2.7.1.37) from sea urchin sperm as purified to near homogeneity and characterized. A 68-fold purification of the enzyme was obtained. This preparation had a specific activity of 389 000 units/mg protein with protamine as the substrate. On the basis of the purification required, it may be calculated that the protein kinase constitutes as much as 1.5% of the soluble protein in sperm. There appeared to be a single form of the enzyme in sea urchin sperm, based on the behavior of the enzyme during DEAE-cellulose and Sephadex G-200 column chromatography. Magnesium ion was required for enzyme activity. The rate of phosphorylation of protamine was stimulated 2.5-fold by an optimal concentration of 0.9 M NaCl. The Km for ATP (minus cyclic AMP) was 0.119 +/- 0.013 (S.D.) and 0.055 mM +/- 0.009 (S.D.) in the presence of cyclic AMP. The specificity of the enzyme toward protein acceptors, in decreasing order of phosphorylation, was found to be histone f1 protamine, histone f2b, histone f3 and histone f2a; casein and phosvitin were not phosphorylated. The holoenzyme was found to have an apparent molecular weight of 230 000 by Sephadex G-200 chromatography. In the presence of 5 - 10(-6) M cyclic AMP, the holoenzyme was dissociated on Sephadex G-200 to a regulatory subunit of molecular weight 165 000 and a catalytic subunit of Mr 73 000. The dissociation could also be demonstrated by disc gel electrophoresis in the presence and absence of cyclic AMP.     

Purification of RNAase II by preparative polyacrylamide gel electrophoresis.

Purification of RNAase II to electrophoretic homogeneity is described. The exonuclease is activated by K+ and Mg2+ and hydrolyses poly(A) to 5'-AMP, exclusively as described by Nossal and Singer (1968, J. Biol. Chem. 243, 913--922). To separate RNAase II from ribosomes, DEAE-cellulose chromatography was used. Two additional chromatographic steps give a preparation that yields 10 bands after analytical polyacrylamide gel electrophoresis. Preparative polyacrylamide gel electrophoresis resulted in a final preparation which on analytical polyacrylamide gels gives a single band. A molecular weight of 76 000 +/- 4000 was obtained from Sephadex G-200 chromatography, with three bands from sodium dodecyl sulfate (SDS) denaturation and SDS gel electrophoresis. The subunits have a molecular weight of 40 000 +/- 2000, 33 000 +/- 2000, and 26 000 +/- 1000. The enzyme thus appears to consist of three dissimilar subunits.     

Molecular structure of aminopeptidase A from bovine kidney

Using gel-filtration through Sephadex G-100 and polyacrylamide gel electrophoresis in the presence of 0,5% sodium dodecyl sulfate, it was found that aminopeptidase A has a molecular weight of 65 000 +/- 2000 and is made up of two subunits with mol. weights of 33 000 +/- 2000. Each subunit consists of two polypeptide chains with mol. weights of 22 000 +/- 2000 and 12 000. During enzyme dissociation into subunits the aspartylnaphtylamidase activity is lost, while the glutamylnaphtylamidase activity is retained.     

Properties of delta5-3beta-hydroxysteroid oxidoreductase isolated from Streptomyces griseocarneus.

Delta5-3beta-hydroxysteroid oxidoreductase was extracted in magnesium-containing Tris buffer from sonicated Streptomyces griseocarneus cells. The enzyme was partially purified (150 X) by ion exchange chromatography and gel filtration following (NH4)2SO4 fractionation. Upon gel filtration on Sephadex G-75 to G-200, the greatest part of the activity gave a peak in the fractionation range. The enzyme obtained from the gel yielded small enzyme molecules on repeated chromatography. A molecular weight of 32 to 36 000 was calculated for the activity appearing in the fractionation range of Sephadex G-75 to G-200. The enzyme is highly specific for the irreversible oxidation of the 3beta-hydroxyl group in steroids with a trans-anellated A : B ring system with either C5 or C6 double bond. Delta5-3-ketosteroids are converted into delta5-3-ketosteroids at a high rate, but the isomerase activity cannot be separated from the oxidoreductase activity either by chromatography or by selective heat inactivation. NAD, NADP, FMN or FAD did not influence the activity, but the enzyme is inactive in the absence of molecular oxygen.     

A novel phosphodiesterase from cultured tobacco cells.

A novel phosphodiesterase was purified from cultured tobacco cells to a state which appeared homogeneous on polyacrylamide gel electrophoresis. The enzyme hydrolyzed various phosphodiester and pyrophosphate bonds, including p-nitrophenyl thymidine 5'-phosphate, p-nitrophenyl thymidine 3'-phosphate, cyclic nucleotides, ATP, NAD+, inorganic pyrophosphate, dinucleotides, and poly(adenosine diphosphate ribose), which is a polymer synthesized from NAD+. However, it did not hydrolyze highly polymerized polynucleotides. The molecular weight of the native enzyme was estimated as 270 000 to 280 000 by gel filtration on Sephadex G-200 and Bio-Gel A-5m. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the enzyme was composed of subunits with molecular weights calculated to be 75 000. The enzyme did not require divalent cations for activity being fully active in the presence of ethylenediaminetetraacetic acid. The pH optimum for the enzyme was approximately 6 with p-ni-trophenyl thymidine 5'-phosphate or adenosine cyclic 3',5'monophosphate, and 5.3 with NAD+. Double reciprocal plots of the initial velocity against the concentration of p-nitrophenyl thymidine 5'-phosphate gave two apparent Km values of 0.17 and 1.3 mM, suggesting the presence of at least two active sites.     

Solubilization of angiotensin I-coverting enzyme from rabbit lung using trypsin treatment.

The solubilization of angiotensin I-converting enzyme (peptidyldipeptide hydrolase, EC 3.4.15.1) from rabbit lung was carried out using trypsin treatment. A good recovery of 76% was obtained. The enzyme from solubilized fraction was purified using colums of Sephadex G-200, hydroxyapatite and DEAE-cellulose. The purified enzyme was shown to convert angiotensin I to angiotensin II and also to inactivate bradykinin. The specific activity of the enzyme was 24.3 units/mg protein for hippurylhistidylleucyl hydroxide and 0.182 mumol/min per mg protein for angiotensin I. The enzymic activity obtained after trypsin treatment for 5 h could be divided into two components: (i) an enzyme of molecular weight 300 000 (peak II) and (ii) an enzyme of molecular weight 145 000 (peak III), by Sephadex G-200 gel filtration. The molecular weight of the denatured enzyme was found to be 155 000 by disc gel electrophoresis in the presence of sodium dodecyl sulfate. Km values of peak II and peak III fraction for Hippuryl-His Leu-OH were 2.6 mM.     

Isolation and partial characterization of secreted mouse pituitary prolactin.

Prolactin secreted by mouse anterior pituitaries was purified by gel filtration on Sephadex G-100. Electrophoretic homogeneity of the purified hormone was demonstrated in several gel systems, and electrophoresis in the presence of sodium dodecyl sulfate indicated an apparent molecular weight of 21 000 +/- 2000. Mouse and ovine prolactin displayed parallel dose vs. response curves in radio-receptor binding studies, indicating that these two hormones compete for identical receptor sites on rabbit mammary membranes. Comparative peptide mapping studies carried out on tryptic digests of mouse and ovine prolactin suggested only partial homology between the two hormones. Internally labeled monomeric mouse prolactin was observed to undergo aggregation following storage at --20 degrees C for 2 months.     

Purification and characterization of human plasma lecithin:cholesterol acyltransferase.

A highly purified (approximately 12 000-fold) homogeneous preparation of human plasma lecithin:cholesterol acyltransferase (LCAT) with 16% yield was obtained by a combination of density ultracentrifugation, high density lipoprotein affinity column chromatography, hydroxylapatite chromatography, and finally chromatography on anti-apolipoprotein D immunoglobulin-Sepharose columns to remove apolipoprotein D. This enzyme preparation was homogeneous by the following criteria: a single band by polyacrylamide gel electrophoresis in 8 M urea; a single band on sodium dodecyl sulfate gel electrophoresis with an apparent molecular weight of 68 000 +/- 1600; a single protein peak with a molecular weight of 70 000 on a calibrated Sephadex G-100 column. Its amino acid composition was different from human serum albumin and all other apoproteins isolated from lipoprotein fractions.     

Characterization of the sex steroid binding protein of human pregnancy serum. Improvements in the purification procedure

The sex steroid binding protein (SBP) of human pregnancy serum was purified to homogeneity by the sequential use of ammonium sulfate precipitation, affinity chromatography on 5alpha-dihydrotestosterone-17beta-succinyldiaminoethyl-(1,4-butanediol diglycidyl ether)-agarose, and preparative polyacrylamide gel electrophoresis. The yield of pure SBP was improved from 5% as originally reported [Mickelson, K. E., and Petra, P. H. (1975), Biochemistry 14, 957] to 34%. Homogeneity of SBP was shown by equilibrium sedimentation ultracentrifugation in 6 M guanidine hydrochloride containing 0.1 M mercaptoethanol which yields a minimum molecular weight of 36 335 +/- 525. The protein is also homogeneous when examined by gel electrophoresis in the presence of sodium dodecyl sulfate. A value of 52 000 for the molecular weight is obtained by this method. SBP partially purified from Cohn fraction IV has also a molecular weight of 52 000 by gel electrophoresis in the presence of sodium dodecyl sulfate; that fraction is contaminated with another protein of molecular weight 90 000 which must be removed to obtain homogeneous SBP. The amino acid composition of SBP isolated from pregnancy serum is presented.     

Physical properties and subunits of DNA dubia erythrocruorin.

The erythrocruorin of the freshwater leech Dina dubia possessed an S20,w of 61 S and exhibited a slightly sigmoid oxygenation curve with n congruent to 1.6 and P50 = 2.4 mm at pH 7.4. A minimum mol. wt of 23 000 +/- 2100 per heme group was determined from the iron and heme contents, 0.22 +/- 0.02 and 2.92 +/- 0.35 weight %. The subunit composition of this erythrocruorin was investigated using polyacrylamide gel electrophoresis and gel filtration in sodium dodecyl sulfate at neutral pH and gel filtration at pH 9. Sodium dodecyl sulfate electrophoresis of Dina erythrocruorin revealed the presence of five subunits (1-5) with mol. wts of about 13 000, 21 000, 23 000, 25 000 and 31 000, respectively. When the erythrocruorin was reduced with mercaptoethanol prior to dodecyl sulfate electrophoresis, three subunits (I-III) were observed, two possessing molecular weights in the range 12 000-14 000 (I and II) and one possessing a molecular weight of about 28 000. One of the subunits I, II, was provided by the dissociation of the 31 000 subunit. Subunit III (28 000) consisted of subunits 2, 3, and 4. It is likely that not all of the polypeptide chains constituting Dina erythrocruorin are associated each with a heme group.     

Structure of beef heart mitochondrial F1-ATPase. Arrangement of subunits as disclosed by cross-linking reagents and selective labeling by radioactive ligands.

1. The following bifunctional reagents, dimethylsuberimidiate, dimethyladipimidate, methylmercaptobutyrimidate have been used to produce dimers between the neighboring subunits of beef heart F1-ATPase. 2. Treatment of beef heart F1-ATPase with dimethylsuberimidate or dimethyladipimidate resulted in the formation of four cross-linked products. Their molecular weights determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were 11 500, 105 000, 95 000 and 80 000, respectively. The products of molecular weight 115 000 and 105 000 were predominant and could be detected at the early stage of the cross-linking reaction. Treatment of beef heart F1-ATPase with methylmercaptobutyrimidate resulted in the accumulation of the product of molecular weight 115 000 and in traces of products of lower molecular weight. When the cross-linked products obtained with methylmercaptobutyrimidate were cleaved by beta-mercaptoethanol, the original gel electrophoresis pattern was restored. 3. Cross-linking of beef heart F1-ATPase by dimethylsuberimidate, dimethyladipimidate and methylmercaptobutyrimidate was accompanied by a loss of the ATPase activity. Cleavage of the cross-linked products obtained with methylmercaptobutyrimidate did not restore the original ATPase activity. 4. Identification of subunits A and B in the products of molecular weight 115 000 and 105 000 was achieved by specific labeling of subunit A with N-[14C]ethylmaleimide and of subunit B by chloronitro [14C]benzooxodiazole. Both products were able to bind N-[14C]ethylmaleimide; only the 105 000 dalton product was able to bind chloronitro [14C]benzooxodiazole. 5. The product of molecular weight 115 000 obtained by treatment of beef heart ATPase with methylmercaptobutyrimidate could bind N-[14C]ethylmaleimide. Its cleavage, following N-[14C]ethylmaleimide binding, yielded one labeled peptide identified with subunit A by polyacrylamide gel electrophoresis. 6. The above results indicate that the product of molecular weight 115 000 is a dimer containing two subunits A and that the product of molecular weight 105 000 is a dimer containing one subunit A and one subunit B. It can therefore be concluded that, in beef heart F1-ATPase, the A subunits are close to each other and that subunit A is close to subunit B. In contrast the B sublnits are probably too far from each other to be cross-linked by dimethylsuberimidate, dimethyladipimidate or methylmercaptobutyrimidate.     

Studies on epsilon-prototoxin of Clostridium perfringens type D. Physicochemical and chemical properties of epsilon-prototoxin.

epsilon-Prototoxin of clostridium perfringens type D consists of one polypeptide chain of 311 amino acids with the following composition: Asp52 Thr31 Ser25 Glu28 Pro12 Gly17 Ala14 Val28 Met5 Ile15 Leu18 Tyr17 Phe8 Lys31 His2 Arg5 Tyr2. It has no free cysteine but contains one blocked cysteine. The N-terminal as well as the C-terminal residue is lysine. The ultracentrifuge pattern gave one single boundary having S020,w = 2.15 S and Do20,w = 5.56-10(-7) cm2/s. Calculation of the molecular weight from D020,w and S020,w gave a value of 34 250. The molecular weight determined from sedimentation equilibrium using ultraviolet optics gave a value of 33 000 +/- 1000. On the other hand molecular weights calculated from a calibrated Sephadex G-100 column in borate buffer was 25 000 and that in sodium phosphate, ionic strength 0.2, was 27 500. This discrepancy between values obtained in the ultracentrifuge and by gel filtration is attributed to adsorption of epsilon-prototoxin by Sephadex.     

alpha-D-galactosidase from soybeans destroying blood-group B antigens. Purification by affinity chromatography and properties.

alpha-D-Galactosidase was isolated from untoasted soybean meal and purified to homogeneity by affinity chromatography on N-epsilon-aminoacaproyl alpha-D-galactopyranosylamine-Sepharose. The purified enzyme destroyed the B-specificity of human ovarian cyst B-glycoprotein with an accompanying increase in H-specificity, and converted human type-B erythrocytes to type O. The enzyme consists primarily of a tetramer, molecular weight 150 000 +/- 5 000 at pH 4.0 and of a monomer, molecular weight 40 000 +/- 3 000 at pH 8.0. Polyacrylamide gel electrophoresis in dodecyl sulfate at pH 7.2 distinguished between two types of monomeric unit of similar molecular weight. N-terminal alanine was identified as the sole N-terminal amino acid residue. The enzyme was shown to be devoid of carbohydrate.     

Further studies on bovine serum amylase. 3. Affinity chromatography

The major bovine serum isoamylases controlled by the AmI locus have been examined by gel filtration. On Sephadex G-200 the isoamylases can be resolved into two classes. The AmI A and AmI B have apparent molecular weights of 307 000 daltons whilst the AmI C isozyme has an apparent molecular weight of 44 400 daltons. The separation of the isozymes into two classes according to their elution behaviour on Sephadex G-200 has been shown to be an affinity separation. All three AmI isozymes are eluted from a non-dextran media (BioGel A1.5m) with apparent molecular weights of 417 000 daltons. The affinity separation on Sephadex G-200 has been shown to be inhibited by the addition of 1% (w/v) maltose to the elution buffer. In the presence of 1 % (w/v) maltose all three AmI isozymes are coeluted from Sephadex G-200 with apparent molecular weights of 321000 daltons. The maltase and amylase activities of the AmI isozymes were eluted coincidentally under all the conditions studied.     

Purification and partial characterization of plasminogen activator from human uterine tissue.

A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen activator from delipidated uterine tissue with 0.3 M potassium acetate buffer, pH 4.2; (2) ammonium sulphate precipitation; (3) zinc chelate-agarose chromatography; (4) n-butyl-agarose chromatography; (5) concanavalin A-agarose chromatography; and (6) gel filtration on Sephadex G-150. The specific activity of the final plasminogen activator preparation was increased by a factor 4500 as compared with the crude extract. The purified plasminogen activator showed a strong tendency to adsorb to surfaces. This could be effectively prevented by Tween-80. The molecular weight of the plasminogen activator was 64 000 as estimated by gel filtration in 1.0 M NaCl and 69 000 as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The plasminogen activator consisted of two chains (molecular weights 31 000 and 38 000) connected by disulphide bridges. The smallest chain contained the serine residue of the active site as deduced from the incorporation of the tritium label of [3H]diisopropylphosphofluoridate.     

An antigen common to a wide range of bacteria. I. The isolation of a 'common antigen' from Pseudomonas aeruginosa

In crude water-soluble extracts of Pseudomonas aeruginosa 64 antigens can be demonstrated by crossed immunoelectrophoresis in agarose with polyvalent Pseudomonas-immunoglobulin. One of these antigens cross-reacts with antigens prepared from bacteria of a wide range of taxonomic groups. Monospecific immunoglobulins to this antigen (Common Antigen) were produced by immunization with the appropriate immunocomplex extracted from agarose. Common Antigen was purified by the combination of two fractionation methods: Precipitation of the crude extract with 18% (w/v) sodium sulfate, followed by gel filtration of the supernatant on a Sephadex G-200 column. By this method, 35% of Common Antigen from the crude extract was recovered, more than half of the fractions electrophoretically pure. Electrophoresis of reduced Common Antigen on a dodecyl sodium sulfate polyacrylamide gel revealed two protein bands with apparent molecular weights of 59-62 000 and 62-65 000, respectively. The untreated antigen, however, passed a column of Sephadex G-200 with the void volumen, indicating a substance of high molecular weight (> 4-600 000).     

Acyl-CoA-ACP-transacylases of Mycobacterium smegmatis. An analytical study

Homogenates of Mycobacterium smegmatis have been prepared by sonication of bacteria in 0,1 M phosphate buffer, pH 7, containing 0,001 M EDTA and 0,01 M 2-mercaptoethanol. The 105 000 g supernatant of these homogenates has been fractionated by ammonium sulfate precipitation. The fraction precipitating between 25 and 65 per cent saturation in ammonium sulfate shows palmityl-CoA-ACP-transacylase, malonyl-CoA-ACP-transacylase and acetyl-CoA-ACP-transacylase activities. These activities are not associated, essentially, to a complexe of high molecular weight as they are retained on the column for 80 per cent or more upon gel filtration.By chromatographic procedures involving Sephadex G-150 gel filtration, and chromatography on DEAE-Sephadex A-50 the malonyl-CoA-ACP-transacylase activity is separated from the other two activities. The palmityl-CoA-ACP-transacylase activity and the acetyl-CoA-ACP-transacylase activity show two close but distinct major peaks either upon gel filtration on Sephadex G-150 or upon DEAE-Sephadex A-50 chromatography indicating thus that these two activities are attribuable to two distinct molecular entities. Besides the major peaks for these two activities, a supplementary minor peak for each activity is observed.An estimate of the approximate range of the apparent molecular weights for palmityl-CoA-ACP-transacylase, malonyl-CoA-ACP-transacylase and acetyl-CoA-ACP-transacylase has been made in using the curve of the K_av values of known proteins plotted against the logarithms of their molecular weights. The molecular weights thus estimated for these three enzymes are 100 000, 32 000 and 85 000 respectively.The void volume fractions of the chromatography of the homogenates on Sephadex G-150 present 20 per cent or less of the enzyme activity of the homogenates. Chromatography of the mixture of the void volume fractions on DEAE-Sephadex A-50 shows that the malonyl-CoA-ACP-transacylase activity associated to these fractions behaves differently from that of the fractions retained upon gel filtration; this may be taken as an indication for the presence of a complexe of the fatty acid synthetase present as a minor component of the homogenates.     

Tamm–Horsfall urinary glycoprotein. The subunit structure

1. Subunit molecular weights of 76000-82000 were obtained for native and alkylated Tamm-Horsfall glycoprotein by gel filtration on Sephadex G-200 in the presence of sodium dodecyl sulphate. 2. A further estimate of the subunit molecular weight of 79000+/-4000 was obtained by disc gel electrophoresis in sodium dodecyl sulphate. 3. A minimum value of the chemical molecular weight of 79000+/-6000 was obtained from the number of N-terminal amino acids released by cyanogen bromide cleavage of the glycoprotein. 4. Similar values were obtained for the subunit molecular weight of Tamm-Horsfall glycoprotein from patients with cystic fibrosis. 5. On ultracentrifugation both in 1.0% sodium dodecyl sulphate and in 70% formic acid, Tamm-Horsfall glycoprotein sedimented as a single component, slightly faster than serum albumin. 6. On reduction of the disulphide bonds the same subunit molecular weight was obtained, which suggested that these bonds are intrachain.     

Purification of (Ca2+-Mg2+)-ATPase from rat liver plasma membranes

The Ca2+-stimulated, Mg2+-dependent ATPase from rat liver plasma membranes was solubilized using the detergent polyoxyethylene 9 lauryl ether and purified by column chromatography using Polybuffer Exchanger 94, concanavalin A-Sepharose 4B, and Sephadex G-200. The molecular weight of the enzyme, estimated by gel filtration in the presence of the detergent on a Sephadex G-200 column, was 200,000 +/- 15,000. The enzyme was purified at least 300-fold from rat liver plasma membranes and had a specific activity of 19.7 mumol/mg/min. Polyacrylamide gel electrophoresis under nondenaturing conditions of the purified enzyme indicated that the enzymatic activity correlated with the major protein band. In sodium dodecyl sulfate-polyacrylamide gel electrophoresis, one major band in the molecular weight range of 70,000 +/- 5,000 was seen. The isoelectric point of the purified enzyme was 6.9 +/- 0.2 as determined by analytical isoelectric focusing. The enzyme was activated by Ca2+ with an apparent half-saturation constant of 87 +/- 2 nM for Ca2+. Calmodulin and trifluoperazine at the concentration of 1 microgram/ml and 100 microM, respectively, had no effect on the enzymatic activity.