Isolation and characterization of two isoperoxidases from tobacco tissue cultures

Two isoperoxidases (A_f and C_n) from the medium of tobacco tissue suspension culture WR-132 grown in darkness have been purified to apparent homogeneity and partially characterized. C_n and A_f have MWs of ca 30 000 and 54 000, respectively. A_f has ca 5.1% carbohydrate, but none could be detected in C_n. Both isoperoxidases appear to follow simple Michaelis-Menten kinetics with respect to guaiacol as the substrate. The K_ms for guaiacol are 4 and 13.3 mM for Af and C_n, respectively, while both isoperoxidases have a pH optimum at 6.5. C_n, is dissimilar to other isoperoxidases from tobacco tissue cultures, but A_f is very similar to isoperoxidase A₃ from W-38 tobacco tissue culture.     

Isoperoxidases from tobacco tissue cultures

Two anodic isoperoxidases (A₁ and A₂) from tobacco tissue culture W-38 and two cathodic isoperoxidases (C₃ and C₄) from tobacco suspension culture WR-132 have been separated and characterized. Molecular weights for each of the isoperoxidases have been determined by two different methods. Only C₄ contained a carbohydrate component. The substrate specificity and the pH optima for the four enzymes with each of five substrates were determined.     

Ferulic acid: a substrate for two isoperoxidases from Nicotiana tabacum tissue cultures

An anodic isoperoxidase (A₂) from tobacco tissue culture W-38 and a cathodic isoperoxidase (C₄) from tobacco tissue suspension culture WR-132 have been separated and characterized. Both isoperoxidases catalysed oxidation of ferulic acid in the presence of H₂O₂. When the reaction mixture was subjected to TLC, ferulic acid was found to have been converted to an unknown compound which, after treatment with ammonia, fluoresces green in UV light. Both the isoperoxidases A₂ and C₄ appear to follow simple Michaelis-Menten kinetics with respect to guaiacol as the substrate. The Kms for guaiacol are 4 and 4·5 mM for isoperoxidases C₄ and A₂, respectively. The pH optimum for both enzymes is about 6·0. The effect of various phenolic and related compounds on the activity of each isoperoxidase is reported and discussed.     

Effect of darkness on isoperoxidases in tobacco tissue cultures

In order to study the effect of light on the tobacco tissue culture WR-132, 5 passages (10 days' growth per passage) of these cells were grown in darkness, and 3 passages were separately grown in intense light (16000 lx). All other growth conditions were the same. The resulting isoperoxidase patterns present in these cells and in their growth media were analyzed at 2-day intervals during this period and then compared with the isoperoxidase patterns of cells grown under dim light conditions (10 lx). A new cathodic isoperoxidase (C_n) appeared in the medium within 2 days after the cells were placed in the dark. C_n was present in all media of WR-132 cell cultures analyzed throughout the 5 passages grown in darkness. The fifth passage in darkness produced total cessation of growth (apparent death). C_n increased and new anodic isoperoxidases A_a, A_b, A_d and A_e appeared in the media as the cells approached death in darkness.     

The effect of amphiphilic peptide surfactants on the light-harvesting complex II

The peptide surfactants are amphiphilic peptides which have a hydrophobic tail and a hydrophilic head, and have been reported to stabilize and protect some membrane proteins more effectively than conventional surfactants. The effects of a class of peptide surfactants on the structure and thermal stability of the photosynthetic membrane protein lightharvesting complex II (LHCII) in aqueous media have been investigated. After treatment with the cationic peptide surfactants A₆K, V₆K₂, I₅K₂ and I₅R₂, the absorption at 436 nm and 470 nm decreased and the absorption at 500–510 nm and 684–690 nm increased. Moreover, the circular dichroism (CD) signal intensity in the Soret region also decreased significantly, indicating the conformation of some chlorophyll (Chl) a, Chl b, and the xanthophyll molecules distorted upon cationic peptide surfactants treatment. The anionic peptide surfactants A₆D and V₆D₂ had no obvious effect on the absorption and CD spectra. Except for A₆D, these peptides all decreased the thermal stability of LHCII, indicating that these peptides may reconstitute protein into a less stable conformation. In addition, the cationic peptide surfactants resulted in LHCII aggregation, as shown by sucrose gradient ultracentrifugation and fluorescence spectra.     

Die Proteinstruktur des RNS-Bakteriophagen fr

Summary The coat protein of the RNA containing bacteriophage f_r has been hydrolyzed and its amino acid composition determined (Table 1). Furthermore, the protein was split with trypsin and the tryptic peptides were separated by column chromatography on Dowex 1 (Figure 1) and purified by paper chromatography and electrophoresis.The amino acid composition of all but one tryptic peptide are given in Table 2. The large peptide T₁₃ which is much more difficult to purify than all other peptides, was isolated by several methods. Its amino acid composition is shown in Table 3. All tryptic peptides are compiled in Table 4.Amino acid sequences have been fully or partially determined for 9 tryptic peptides (Table 5) and the others are presently being investigated.These findings are compared with the results from other RNA phages, especially f₂. It is concluded from the available data that the relationship between the coat proteins of the RNA phages is similar to that between the various naturally occurring strains of tobacco mosaic virus whose amino acid sequences are known.

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Herrn Prof.G. Melchers zum 60. Geburtstag gewidmet.     

Ribonuclease activities in bean roots

Vicia faba meristematic and elongating root cells (zones 0–4 and 10–20 mm) contained one nuclease (A₁) and four ribonucleases (A₂, A₃, C₁, C₂). When the overall activity of each enzyme was expressed per cell, the elongating cells contained 4-, 4-, 4-, 10- and 17-fold more activity than meristematic cells for A₁, C₁, C₂, A₂ and A₃, respectively.     

Novel Peptide Inhibitors of β-Catenin Effectively Suppress the Tumorigenesis of Colorectal Cancer

Aberrant β-catenin activation promotes the proliferation and survival of several types of tumor cells, including colorectal cancer (CRC) cells. Synthetic peptides are drug candidates for treating various diseases; however, peptide inhibitors of β-catenin have been rarely reported. A series of peptide inhibitors for β-catenin (F15A_1–9k, F15A_2–9k, and F15A_3–9k) were designed and synthesized, and then used to treat human CRC cells (HT-29). Next, a series of in vitro assays, including cell counting, colony formation, flow cytometry, and Transwell assays, were performed to assess the biological effects of the peptides on CRC cells. Mouse xenograft models of HT-29 tumors were also used to evaluate the inhibitory effect of the peptide inhibitors on β-catenin expression in vivo. The inhibitory effect of the peptide inhibitors on β-catenin production was tested in a confocal laser scanning microscope study (CLSMS), and by H&E, TUNEL, and immunohistochemical (IHC) staining. The peptide inhibitors significantly reduced the viability of HT-29 cells in time- and concentration-dependent manners. Moreover, the peptide inhibitors for β-catenin significantly inhibited CRC tumorigenesis both in vitro and in vivo. Mechanistically, the peptide inhibitors for β-catenin inhibited the angiogenesis activity of HT-29 cells. When administered by itself, F15A_2–9k blocked cell division, induced apoptosis, and reduced the migration and invasion capabilities of HT-29 cells, while a combination of F15A_1–9k, F15A_2–9k, and F15A_3–9k showed even stronger inhibitory effects on HT-29 cells. In summary, the peptides designed to inhibit β-catenin demonstrated anti-tumor activity both in vitro and in vivo, suggesting their potential as therapeutic agents for treating CRC.

     

Fullerene‐based inhibitors of HIV‐1 protease

A series of Fmoc‐Phe(4‐aza‐C₆₀)‐OH of fullerene amino acid derived peptides have been prepared by solid phase peptide synthesis, in which the terminal amino acid, Phe(4‐aza‐C₆₀)‐OH, is derived from the dipolar addition to C₆₀ of the Fmoc‐Nα‐protected azido amino acids derived from phenylalanine: Fmoc‐Phe(4‐aza‐C₆₀)‐Lys₃‐OH ( 1 ), Fmoc‐Phe(4‐aza‐C₆₀)‐Pro‐Hyp‐Lys‐OH ( 2 ), and Fmoc‐Phe(4‐aza‐C₆₀)‐Hyp‐Hyp‐Lys‐OH ( 3 ). The inhibition constant of our fullerene aspartic protease PRIs utilized FRET‐based assay to evaluate the enzyme kinetics of HIV‐1 PR at various concentrations of inhibitors. Simulation of the docking of the peptide Fmoc‐Phe‐Pro‐Hyp‐Lys‐OH overestimated the inhibition, while the amino acid PRIs were well estimated. The experimental results show that C₆₀‐based amino acids are a good base structure in the design of protease inhibitors and that their inhibition can be improved upon by the addition of designer peptide sequences. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.     

Studies on cyclic peptides. II. Synthesis of cyclic peptides containing sarcosine.

Cyclic peptides containing sarcosine, cyclo-(Pro-Sar-Gly)₂, cyclo-(Sar-Sar-Gly)₂, cyclo-(Sar₄), and cyclo-(Sar₆) have been synthesized by the cyclization of the p-nitrophenyl ester of linear peptides. The tert-butoxycarbonyl group was used as the N^α-protecting group, which was removed by acid. Benzyl ester was used to protect the C-terminal. tert-butoxycarbonylpeptide was obtained by the stepwise elongation of the peptide bond by the carbodiimide method. Deblocking and cyclization of the linear peptides gave the cyclic peptides.     

Distribution and regulation of natriuretic factor-R1C receptor subtypes in mammalian cell lines

The differential distribution of natriuretic peptide receptor subtypes and their distinct properties were assessed in mammalian cellular models which were screened for their ability to produce cGMP upon stimulation by different natriuretic peptides. The ANF-R_1A receptor subtype was distinguished by its selective activation by atrial natriuretic factor (ANF) while the ANF-R_1C was characterized by preferential stimulation by C-type natriuretic peptide (CNP). AT-t20 pituitary cells, bovine adrenal chromaffin cells, and NIH-3T3 fibroblasts mainly express the ANF-R_1C receptor subtype. Other cell lines such as PC12, RASM and GH3 express significant but varying amounts of both ANF-R_1A and ANF-R_1C subtypes. A10 and NIH cells which express high density of ANF-R₂ receptor subtype, also demonstrate a higher sensitivity to CNP over ANF suggesting that they express significant amounts of ANF-R_1C. Studies of the regulation by ATP of guanylyl cyclase activity indicate that both ANF-R_1A and ANF-R_1C subtypes are modulated in the same manner. In the presence of Mn²⁺, ATP inhibits the CNP-stimulated guanylyl cyclase activity while in the presence of Mg²⁺ adenine nucleotides potentiate the stimulation by CNP. In addition, we show that like the ANF-R_1A, the ANF-R_1C guanylyl cyclase activity can be regulated by phosphorylation since preincubation with TPA or FKL attenuates the subsequent stimulation by CNP in cultured cells. The results presented demonstrate that specific cell types express distinct natriuretic peptide receptor subtypes and also that the newly characterized ANF-R_1C subtype is regulated by ATP and serine/threonine kinases in the same way as the ANF-R_1A subtype.Abbreviation ANF atrial natriuretic factor - BNP brain natriuretic peptide - CNP C-type natriuretic peptide - ATP adenosine-5-triphosphate - IBMX 3-isobutyl-1-methylxanthine - TPA 12-O-tetradecanoyl-phorbol-13-acetate - FKL forskolin - PKC calcium-phospholipid-dependent protein kinase - PKA cAMP-dependent protein kinase - PKG cGMP-dependent protein kinase - C-ANF [Cys¹¹⁶]-ANF-(102-116)-NH₂ - CC chromaffin cells     

FOUR PROTEIN POLYMORPHISMS IN PIGEON BRAIN EXTRACTS DETECTED BY TWO-DIMENSIONAL GEL ELECTROPHORESIS

Abstract— Proteins of the brain extracts of 85 individual pigeons (Columba livia) were mapped by two-dimensional gel electrophoresis. The method is a modification of O'Farrell 'S technique and separates proteins first by charge and then by molecular weight. There were three proteins, A, B and D which had each a variant form. The positions of these six proteins on the gel corresponded to the following pH values and molecular weight values: protein A₁, 6.4/43,000; A₂, 6.6/43,000; B₁, 5.7/41,000; B₂, 5.8/40,000; D₁, 6.2/22,000; D₂, 6.2/21,000. The variants are genetically determined, since protein A, B and D each occurred in three phenotypes (A₁, A₁A₂ and A₂; B₁, B₁B₂ and B₂; D₁, D₁D₂ and D₂) corresponding to the three possible genotypes. From the observed frequencies of the phenotypes the following allele frequencies were calculated: allele A₁, 72%; A₂, 28%; B₁, 15%; B₂, 85%; D₁, 74%; D₂, 26%. A fourth protein named C occurred in four different forms (C₁, 7.2/37,000; C₂, 7.2/36,000; C₃, 7.1/37,000; C₄, 7.1/36,000) and six phenotypes (C₁, C₁C₂, C₂, C₁C₃, C₂C₃ and C₄C₃). This polymorphism is also interpreted as being genetically determined. The four alleles coding for the four protein C forms had the following frequencies: allele C₁, 62%; C₂, 27%; C₃, 10.5%; C₄, 0.5%.     

Specificity of Phage Display Selected Peptides for Modified Anticodon Stem and Loop Domains of tRNA

Protein recognition of RNA has been studied using Peptide Phage Display Libraries, but in the absence of RNA modifications. Peptides from two libraries, selected for binding the modified anticodon stem and loop (ASL) of human tRNA^Lys3 having 2-thiouridine (s²U₃₄) and pseudouridine (Ψ₃₉), bound the modified human ASL^Lys3(s²U₃₄;Ψ₃₉) preferentially and had significant homology with RNA binding proteins. Selected peptides were narrowed to a manageable number using a less sensitive, but inexpensive assay before conducting intensive characterization. The affinity and specificity of the best binding peptide (with an N-terminal fluorescein) were characterized by fluorescence spectrophotometry. The peptide exhibited the highest binding affinity for ASL^Lys3(s²U₃₄;Ψ₃₉), followed by the hypermodified ASL^Lys3 (mcm⁵s²U₃₄;ms²t⁶A₃₇) and the unmodified ASL^Lys3, but bound poorly to singly modified ASL^Lys3 constructs (Ψ₃₉, ms²t⁶A_37, s²U₃₄), ASL^Lys1,2 (t⁶A₃₇) and Escherichia coli ASL^Glu (s²U₃₄). Thus, RNA modifications are potentially important recognition elements for proteins and can be targets for selective recognition by peptides.     

1,3-Dialkyl-substituted tetrahydropyrimido[1,2-f]purine-2,4-diones as multiple target drugs for the potential treatment of neurodegenerative diseases

Adenosine receptors and monoamine oxidases are drug targets for neurodegenerative diseases such as Parkinson’s and Alzheimer’s disease. In the present study we prepared a library of 55 mostly novel tetrahydropyrimido[2,1-f]purinediones with various substituents in the 1- and 3-position (1,3-dimethyl, 1,3-diethyl, 1,3-dipropyl, 1-methyl-3-propargyl) and broad variation in the 9-position. A synthetic strategy to obtain 3-propargyl-substituted tetrahydropyrimido[2,1-f]purinedione derivatives was developed. The new compounds were evaluated for their interaction with all four adenosine receptor subtypes and for their ability to inhibit monoamine oxidases (MAO). Introduction of mono- or di-chloro-substituted phenyl, benzyl or phenethyl residues at N9 of the 1,3-dimethyl series led to the discovery of a novel class of potent MAO-B inhibitors, the most potent compound being 9-(3,4-dichlorobenzyl)-1,3-dimethyl-6,7,8,9-tetrahydropyrimido[1,2-f]purine-2,4(1H,3H)-dione (21g, IC₅₀ human MAO-B: 0.0629 μM), which displayed high selectivity versus the other investigated targets. Potent dually active A₁/A_2A adenosine receptor antagonists were identified, for example, 9-benzyl-1-methyl-3-propargyl-6,7,8,9-tetrahydropyrimido[1,2-f]purine-2,4(1H,3H)dione (19f, K_i, human receptors, A₁: 0.249 μM, A_2A: 0.253 μM). Several compounds showed triple-target inhibition, the best compound being 9-(2-methoxybenzyl)-1-methyl-3-(prop-2-ynyl)-6,7,8,9-tetrahydro pyrimido [1,2-f]purine-2,4(1H,3H)-dione (19g, K_i A₁: 0.605 μM, K_i A_2A: 0.417 μM, IC₅₀ MAO-B: 1.80 μM). Compounds inhibiting several different targets involved in neurodegeneration may exhibit additive or even synergistic effects in vivo.     

Two-Component Anti-Staphylococcus aureus Lantibiotic Activity Produced by Staphylococcus aureus C55

Staphylococcus aureus C55 was shown to produce bacteriocin activity comprising three distinct peptide components, termed staphylococcins C55α, C55β, and C55γ. The three peptides were purified to homogeneity by a simple four-step purification procedure that consisted of ammonium sulfate precipitation followed by XAD-2 and reversed-phase (C₈ and C₁₈) chromatography. The yield following C₈ chromatography was about 86%, with a more-than-300-fold increase in specific activity. When combined in approximately equimolar amounts, staphylococcins C55α and C55β acted synergistically to kill S. aureus or Micrococcus luteus but not S. epidermidis strains. The N-terminal amino acid sequences of all three peptides were obtained and staphylococcins C55α and C55β were shown to be lanthionine-containing (lantibiotic) molecules with molecular weights of 3,339 and 2,993, respectively. The C55γ peptide did not appear to be a lantibiotic, nor did it augment the inhibitory activities of staphylococcin C55α and/or C55β. Plasmids of 2.5 and 32.0 kb are present in strain C55, and following growth of this strain at elevated temperature (42°C), a large proportion of the progeny failed to produce strong bacteriocin activity and also lost the 32.0-kb plasmid. Protoplast transformation of these bacteria with purified 32-kb plasmid DNA regenerates the ability to produce the strong bacteriocin activity.     

Syntheses, electrolytic behaviour and antifungal activities of Zn(II) complexes of isomers of 3,10-C-meso-3,5,7,7,10,12,14,14-octamethyl-1,4,8,11-tetraazacyclotetradecane (L). Crystal and molecular structure of [ZnLB(NO3)]NO3 (LB = a,e,a,e-L)

The isomeric cyclam ligands Me₈[14]anes, designated by L_A, L_B and L_C, produce, on reaction with zinc(II)nitrate, zinc(II)sulphate or zinc(II)chloride corresponding complexes, i.e. dinitrato/mononitrato-nitrate complexes [ZnL(NO₃)₂]/[ZnL(NO₃)](NO₃) (L = L_A, L_B or L_C, where the indices A, B and C refer to differing orientations of the four methyl groups on secondary carbons of Me₈[14]ane)_, the diaqua-sulphates [ZnL(H₂O)₂]SO₄ (L = L_A, L_B or L_C), and the diaqua dichloride and dichlorido complexes [ZnL(H₂O)₂]Cl₂ (L = L_A or L_C) or [ZnL_BCl₂], respectively. The complexes have been characterised on the basis of elemental analyses, IR, UV-Vis, ¹H and ¹³C NMR spectroscopies, magnetic and conductance data. The structure of [ZnL_B(NO₃)](NO₃) has been determined by X-ray crystallography. The zinc centre is coordinated to a N₄O donor set in a square-pyramidal geometry. The complexes show differing electrolytic behaviour in different solvents. In chloroform, the complexes are non-electrolytes, indicating that both anions are coordinated to Zn²⁺. Antifungal activity of the ligands and complexes against the phytopathogenic fungi Alternaria alternata and Colletotrichum corcolei have been investigated, and positive results were noted.     

Molecular mechanisms of interaction of polycationic peptides with serpentine type receptors and heterotrimeric G-proteins in rat tissues

The key step in the hormonal signal transduction into cell is interaction of receptors with heterotrimeric G-proteins. We and other authors have shown that G-proteins may be activated as a result of their direct interaction with polycationic peptides. The goal of this work was to study molecular mechanisms of effect of hydrophobic peptide I, C-εAhx-WKK(C₁₀)-KKK(C₁₀)-KKKK(C₁₀)-YKK(C₁₀)-KK, and branched peptide II, [(GRGDSGRKKRRQRRRPPQ)₂-K-εAhx-C]₂ including the 48–60 fragment of the HIV-1 TAT-protein, on receptor and G-protein. These two peptides (10^?6?10^?4 M) produced a dose-dependent simulation of the GTP-binding activity of G-proteins in plasma membrane fractions of the brain striatum and cardiac muscle in rats. The effect of peptide I was more pronounced and decreased to a considerable degree in the presence of the C-terminal 385–394 peptide of the G-protein α_s-subunit that selectively disrupts interaction of receptors with G_s-protein. Peptide I reduced markedly affinity of serotonin (agonist) to the serotonin striatum receptors, whereas peptide II inhibited to the significant extent the binding of dihydroalprenolol (antagonist) to β-adrenergic receptors in cardiac muscle. Peptide I, unlike peptide II, decreased essentially the high affinity binding of β-agonist isoproterenol. The obtained data indicate the ability of polycationic peptides to activate G₁-proteins, to disturb their coupling with receptor, and to affect binding properties of the receptor. There are differences in molecular mechanisms of action of peptides with different structures on G-proteins and receptors.     

Conformations of cyclic peptide/calcium complexes in solution

Synthetic cyclic octapeptides of general structure cyclo[Glu(γOBzl)-Sar-Gly-(N-R)Gly]₂ (R = n-hexyl and cyclohexyl) transport calcium ions selectively across organic phases and phospholipid membranes. We have now used proton nmr spectroscopy (360 MHz) to study the solution conformation(s) of their calcium complexes. When Ca(ClO₄)₂ was added to solutions of these peptides in CDCl₃, nmr spectra of the resulting calcium complexes were characteristic of a single C₂-symmetric conformer. From a Karplus-Bystrov analysis of vicinal coupling constants in both the peptide backbone and Glu side chain (treated as an ABCC′MX spin system), in conjuction with model-building studies, a structure was proposed in which the calcium ion is bound in an octahedral-type complex by the four (coplanar) carbonyl groups of the (all-trans) Glu-Sar and Gly-(N-R)Gly peptide bonds. Occurrence of preferred rotamers about Glu side chain C^α–C^β bonds indicated that restricted rotation in peptide side chains arises upon calcium binding.     

8-Substituted 1,3-dimethyltetrahydropyrazino[2,1-f]purinediones: Water-soluble adenosine receptor antagonists and monoamine oxidase B inhibitors

Multitarget approaches, i.e., addressing two or more targets simultaneously with a therapeutic agent, are hypothesized to offer additive therapeutic benefit for the treatment of neurodegenerative diseases. Validated targets for the treatment of Parkinson’s disease are, among others, the A_2A adenosine receptor (AR) and the enzyme monoamine oxidase B (MAO-B). Additional blockade of brain A₁ ARs may also be beneficial. We recently described 8-benzyl-substituted tetrahydropyrazino[2,1-f]purinediones as a new lead structure for the development of such multi-target drugs. We have now designed a new series of tetrahydropyrazino[2,1-f]purinediones to extensively explore their structure–activity-relationships. Several compounds blocked human and rat A₁ and A_2AARs at similar concentrations representing dual A₁/A_2A antagonists with high selectivity versus the other AR subtypes. Among the best dual A₁/A_2AAR antagonists were 8-(3-(4-chlorophenyl)propyl)-1,3-dimethyl-6,7,8,9-tetrahydropyrazino[2,1-f]purine-2,4(1H,3H)-dione (41, K_i human A₁: 65.5 nM, A_2A: 230 nM; K_i rat A₁: 352 nM, A_2A: 316 nM) and 1,3-dimethyl-8-((2-(thiophen-2-yl)thiazol-4-yl)methyl)-6,7,8,9-tetrahydropyrazino[2,1-f]purine-2,4(1H,3H)-dione (57, K_i human A₁: 642 nM, A_2A: 203 nM; K_i rat A₁: 166 nM, A_2A: 121 nM). Compound 57 was found to be well water-soluble (0.7 mg/mL) at a physiological pH value of 7.4. One of the new compounds showed triple-target inhibition: (R)-1,3-dimethyl-8-(2,1,3,4-tetrahydronaphthalen-1-yl)-6,7,8,9-tetrahydropyrazino[2,1-f]purine-2,4(1H,3H)-dione (49) was about equipotent at A₁ and A_2AARs and at MAO-B (K_i human A₁: 393 nM, human A_2A: 595 nM, IC₅₀ human MAO-B: 210 nM) thus allowing future in vivo explorations of the intended multi-target approach.     

Active center and subunit structure of transaldolase from Candida utilis.

Crystalline transaldolase (type III) isolated from Candida utilis is composed of two identical subunits, as shown by the following lines of evidence. 1. Tryptic digestion of the performic acid oxidized enzyme yields the number of ninhydrin- and arginine-positive peptides expected for identical subunits. 2. All attempts to separate both subunits by molecular weight or charge differences have failed. 3. Cyanogen bromide cleavage and sodium dodecyl sulfate gel electrophoresis of S-carboxymethylated transaldolase revealed four distinct peptides designated C₂ to C₅ according to their decreasing molecular weight and one additional peak, C₁, in low yield, presumably an aggregate or partially degraded peptide.By chromatography on Sephadex G-100 the maleylated cyanogen bromide digest from ¹⁴C-labeled β-giyceryl-transaldolase could be separated into four peptide peaks which have been analyzed for their amino acid composition. The largest peptide C₂ with a molecular weight of 16,800 was identified as the active site containing fragment. The four fragments together account for all amino acid residues in the entire protein.From transaldolase (type I) containing four methionine residues three cyanogen bromide peptides could be identified. By addition of the individual peptides a molecular weight of 37,100 ± 3500 could be calculated, which is half the molecular weight of the native enzyme. From experimental data presented so far both isoenzymes of transaldolase can be regarded as “half-of-the-sites” enzymes.