Mixed Function Oxidase Inhibitors Protect Plants from Ozone Injury

κ-Casein and α_s1-κ-casein complex with a weight ratio of unity were dissolved in 50mm cacodylate-HCl-70 mm KC1 buffer containing 0.02% of sodium azide (pH 7.1), and their size and shape in the absence and/or presence of calcium ions were observed with the electron microscope. In the absence of calcium ions, both κ-casein and α_s1-κ-casein complex were spherical particles. However, the mean length of α_s1-κ-casein complex (12 nm) was smaller than that of κ-casein (17 nm), which suggested that complex formation led to dissociation of the κ-casein polymer. The addition of calcium ions to the complex led to the formation of bent chains, though micelle-like aggregates were not observed even at 20 nm calcium. Comparison of the frequency distributions of α_s1-κ-casein complex at 0, 5, 10, 15 and 20 mm of calcium with the calculated probability distributions suggested that most α_s1-κ-casein complexes had two binding sites above 10 mm of calcium, which seemed to be essential for the stability of casein micelle.     

Effect of 1-Anilino-8-naphthalenesulfonate on Properties and Associations of αs-, β- and κ-Caseins

It was indicated from fluorescence spectra and fluorescence titration that a hydrophobic probe, 1-anilino-8-naphthalenesulfonate (ANS), binds to casein components (α_s-, β- and κ-caseins). Fluorescence intensity and affinity of ANS-κ-casein complex were larger than that of ANS-α_s- and ANS-β-casein complexes. Enhancements of fluorescence intensity of complexes of casein components were observed by the addition of KCI or CaCl₂. Reason for the enhancement was postulated to be the increase of the quantum yield of the ANS fluorescence caused by the environmental change of ANS binding region of the casein components.

Marked increase of sedimentation coefficient of β-casein in the presence of KCl or CaCl₂ at 10°C was caused by the addition of ANS. This may be responsible for the stimulation of the Ca-dependent precipitation of β-casein by the addition of ANS.

It was found that α_s · κ-association was prevented by ANS and that hydrophobic interaction have an important role for α_s · κ-association.     

Studies on κ-Casein of Bovine Milk

κ-Caseins were prepared by the calciurn-ethanol method, the Sephadex method and the urea-sulfuric acid method. Some important properties of κ-caseins were investigated using isoelectric focusing, starch gel electrophoresis, ultracentrifugation, chemical analysis, stabilization test of α_s-casein, and rennin treatment. Isoelectric focusing established that κ-casein had its isoelectric point near pH 6.0 in 6 m urea, usually accompanied by a second peak around pH 5.6. Ultracentrifugation, however, showed a single peak having a s_20,w value of 2.6 ~ 3.8 in the presence of 6 m urea and of 14.4 in the absence of such dispersing reagents. Normal contents of hexose, sialic acid, phosphorus, and nitrogen were about 1.5, 0.8, 0.2, and 14%, respectively. Relative patterns of amino acid composition were similar in all of the κ-caseins. In addition, amino acid composition in intact κ-casein and in the further purified κ-casein which formed the second peak in DEAE cellulose chromatography were almost identical, indicating that the κ-casein of the first peak is not an impurity but is one of the components which formed the original κ-casein complexes. The ability of κ-caseins to stabilize α_s-casein in the presence of calcium increased when purified by DEAE cellulose chromatography.     

Isolation of Dehydro-ipomeamarone,a New Sesqui-terpenoid from the Black-rot Fungus Infected Sweet Potato Root Tissue and Its Relation to the Biosynthesis of Ipomeamarone

α_s1-Casein was dissolved in 50 mm cacodylate-HCl-70 mm KC1 buffer containing 0.02% of sodium azide (pH 7.1), and the size and shape of α_s1-caseins in the absence and presence of calcium ions were observed with the electron microscope. In the absence of calcium ions, most α_s1-caseins existed as spherical particles of which the smallest diameter was 5~6 nm. The particles were polymerized into bent chains by adding 3 mm calcium. It seemed that the smallest particles were the polymerizing units. The mean length of α_s1-casein in the absence of calcium was 8.7 nm, and it increased as the calcium concentration increased. From these results, it was speculated that α_s1-casein in the absence of calcium had one binding site and the calcium-induced conformational changes produced a second binding site. The probability distributions were calculated with the above speculation, and compared with the frequency distributions obtained from electron micrographs. It was suggested from the comparisons that the second binding site produced in α_s1-casein might be responsible for the calcium-induced aggregation.     

Structure of Bovine κ-Casein: Spectrophotometric Titration and Molecular Size Changes in Alkaline Solution

The ionization of tyrosyl groups in bovine κ-casein and S-carboxyamidomethyl-κ-casein (CAM-κ) was studied by spectrophotometric titration at 295 mµ. In the denaturing solvent 8 m urea, the titration curves are reversible and the pK_app values of eight tyrosyl groups both in κ-casein and in CMA-κ-casein are 10.7. In 0.2 m KCl solution, κ-casein has six tyrosyl groups with normal pK_app value of 10.5 and two groups with higher pK_app value of 11.4. CAM-κ-casein has eight tyrosyl groups with pK_app value of 10.6 in 0.2 m KCl solution. These observations suggest that -S-S- bondings in κ-casein are concerned with the ‘masking’ of the tyrosyl groups. The evidence of the rupture of intermolecular -S-S- bondings of κ-casein in alkaline solution was shown by the study of gel Chromatograph y on Sephadex G–150. One of the possible explanation is that the ionization of tyrosyl groups with higher pK_app value is associated with the destruction of hydrophobic regions, and this destruction is due to the rupture of intermolecular -S-S- bondings under alkaline conditions.     

Quantification of Physical and Cyto-physiological Conditions for the Electrofusion of Saccharomyces cerevisiae

Various conditions for obtaining hybrids of the auxotrophic mutants SH1509 and SH1512 of Saccharomyces cerevisiae by electrofusion were investigated. An AC field of 400 V_p/cm and a DC field of 2 square pulses (7 kV/cm; 60/βsec each) at an interval of 0.5 sec were effective. Treatment with 0.2 (SH1509) or l.0 mg/ml (SH1512) Zymolyase for 1 or 1.5 hr was essential. As to the molarity of the osmotic stabilizer (sorbitol), the hybrid yield peaked at 0.6 m. The presence of CaCl₂ (up to 0.4 mm) or 0.1 mm CaCl₂ with 0.1 mm MgCl₂ enhanced the yield. The temperature of the spheroplast suspension during pulsations also affected the yield, the most suitable temperature being 28°C.     

Characterization of a Cellobiose Phosphorylase from a Hyperthermophilic Eubacterium,Thermotoga maritima MSB8

The cepA putative gene encoding a cellobiose phosphorylase of Thermotoga maritima MSB8 was cloned, expressed in Escherichia coli BL21-codonplus-RIL and characterized in detail. The maximal enzyme activity was observed at pH 6.2 and 80°C. The energy of activation was 74 kJ/mol. The enzyme was stable for 30 min at 70°C in the pH range of 6-8. The enzyme phosphorolyzed cellobiose in an random-ordered bi bi mechanism with the random binding of cellobiose and phosphate followed by the ordered release of D-glucose and α-D-glucose-1-phosphate. The K _m for cellobiose and phosphate were 0.29 and 0.15 mM respectively, and the k _cat was 5.4 s^-1. In the synthetic reaction, D-glucose, D-mannose, 2-deoxy-D-glucose, D-glucosamine, D-xylose, and 6-deoxy-D-glucose were found to act as glucosyl acceptors. Methyl-β-D-glucoside also acted as a substrate for the enzyme and is reported here for the first time as a substrate for cellobiose phosphorylases. D-Xylose had the highest (40 s^-1) k _cat followed by 6-deoxy-D-glucose (17 s^-1) and 2-deoxy-D-glucose (16 s^-1). The natural substrate, D-glucose with the k _cat of 8.0 s^-1 had the highest (1.1×10⁴ M^-1 s^-1) k _cat/K _m compared with other glucosyl acceptors. D-Glucose, a substrate of cellobiose phosphorylase, acted as a competitive inhibitor of the other substrate, α-D-glucose-1-phosphate, at higher concentrations.     

Antitumor Activities and Immunochemical Properties of the Cell-wall Polysaccharides from Aureobasidium pullulans

Delipidated cell walls from Aureobasidium pullulans were fractionated systematically.

The cell surface heteropolysaccharide contains D-mannose, D-galactose, D-glucose, and D-glucuronic acid (ratio, 8.5:3.9:1.0:1.0). It consists of a backbone of (1→6)-α-linked D-mannose residues, some of which are substituted at O-3 with single or β-(1→6)-linked D-galactofuranosyl side chains, some terminated with a D-glucuronic acid residue, and also with single residues of D-glucopyranose, D-galactopyranose, and D-mannopyranose.

This glucurono-gluco-galactomannan interacted with antiserum against Elsinoe leucospila, which also reacted with its galactomannan, indicating that both polysaccharides contain a common epitope, i.e., at least terminal β-galactofuranosyl groups and also possibly internal β-(1→6)-linked galactofuranose residues.

It was further separated by DEAE-Sephacel column chromatography to gluco-galactomannan and glucurono-gluco-galactomannan.

The alkali-extracted β-D-glucan was purified by DEAE-cellulose chromatography to afford two antitumor-active (1→3)-β-D-glucans. One of the glucans (M_r, 1–2 × 10⁵) was a O-6-branched (1→3)-β-D-glucan with a single β-D-glucosyl residue, d.b., 1/7, and the other (M_r, 3.5–4.5 × 10⁵) had similar branched structure, but having d.b., 1/5. Side chains of both glucans contain small proportions of β-(1→6)-and β-(1→4)-D-glucosidic linkages.     

Purification and Characterization of β-N-Acetylhexosaminidase from the Liver Prawn,Penaeus japonicus

β-N-Acetvlhexosaminidase (EC 3.2.1.52) was purified from the liver of a prawn, Penaeus japonicus, by ammonium sulfate fractionation and chromatography with Sephadex G-100, hydroxylapatite, DEAE-Cellulofine, and Cellulofine GCL-2000-m. The purified enzyme showed a single band keeping the potential activity on both native PAGE and SDS–PAGE. The apparent molecular weight was 64,000 and 110,000 by SDS–PAGE and gel filtration, respectively. The pI was less than 3.2 by chromatofocusing. The aminoterminal amino acid sequence was NH₂-Thr-Leu-Pro-Pro-Pro-Trp-Gly-Trp-Ala-?-Asp-Gln-Gly-VaI-?-Val-Lys-Gly-Glu-Pro-. The optimum pH and temperature were 5.0 to 5.5 and 50°C, respectively. The enzyme was stable from pH 4 to 11, and below 55°C. It was 39% inhibited by 10mM HgCl₂.

Steady-state kinetic analysis was done with the purified enzyme using N-acetylchitooligosaccharides (GlcNAc_n, n = 2 to 6) and p-nitrophenyl N-acetylchitooligosaccharides (pNp-β-GlcNAc_n, n= 1 to 3) as the substrates. The enzyme hydrolyzed all of these substrates to release monomeric GlcNAc from the non-reducing end of the substrate. The parameters of K_m and k_cat at 25°C and pH 5.5 were 0.137 mM and 598s^–1 for pNp-β-GlcNAc, 0.117 mM and 298s^–1 for GlcNAc₂, 0.055 mM and 96.4s^–1 for GlcNAc₃, 0.044 mM and 30.1 s^–1 for GlcNAc_4, 0.045 mM and 14.7 s^–1 for GlcNAc₅, and 0.047 mM and 8.3 s^–1 for GlcNAc₆, respectively. These results suggest that this β-N-acetylhexosaminidase is an exo-type hydrolytic enzyme involved in chitin degradation, and prefers the shorter substrates.     

Kinetic Studies on Xylanase Induction by β-Xyloside in Streptomyces sp.

Xylanase induction by β-xyloside was investigated in non-growing conditions using non-induced mycelia of Streptomyces sp. No. 3137 harvested from glucose medium. The mycelia started to produce xylanase without lag time when β-xyloside was added. The rate of xylanase synthesis was dependent on the concentration of β-xyloside added to the inducing culture medium. The induction constants of various β-xylosides were calculated from the Lineweaver-Burk plots; those of methyl-, isopropyl-, butyl- and ethylencyanohydrin-β-d-xylosides were 10.53 mm, 3.83 mm, 0.55mm and 0.25 mm, respectively. Some α-xylosides repressed xylanase synthesis. The rate of xylanase synthesis decreased suddenly after the addition of α-xyloside. The inhibition constants of methyl-, ethyl- and isopropyl-α-d-xylosides were 8.80 mm, 12.50 mm and 33.33 mm, respectively. The xylanase induction was also repressed by glucose. However, this repression was completely restored after consuming additional glucose.     

Studies on the Interaction between αs1- and β-Caseins

The interaction of α_s1-casein with β-, dephosphorylated β-,γ- and R-caseins was studied. It was proved by the sedimentation velocity experiments that α_s1-casein formed a complex with each of these components at 25±C in the presence of 3 mm CaCl₂.

In the presence of 10 mm CaCl₂, β- and dephosphorylated β-casein prevented the precipitation of α_s1-casein and gave micelle-like turbid solutions. However, γ- and R-caseins, fragments of β-casein, did not stabilize α_s1-casein. It was concluded from these results that α-casein interacted with α_s1-casein through its hydropholic region corresponding to R-casein and that hydrophilic region of β-casein was responsible for the stabilization of α_s1-casein.     

Substrate Specificity of α-Glucosidase II in Rice Seed

The substrate specificity of rice α-glucosidase II was studied. The enzyme was active especially on nigerose, phenyl-α-maltoside and maltooligosaccharides. The actions on isomaltose and phenyl-α-glucoside were weak, and on sucrose and methyl-α-glucoside, negligible. The α-glucans, such as soluble starch, amylopectin, β-limit dextrin, glycogen and amylose, were also hydrolyzed.

The ratio of the maximum velocities for hydrolyses of maltose (G₂), nigerose (N), kojibiose (K), isomaltose (I), phenyl-α-maltoside (?M) and soluble starch (SS) was estimated to be 100: 94.4: 14.2: 7.1: 89.5: 103.1 in this order, and that for hydrolyses of malto-triose (G₃), -tetraose (G₄), -pentaose (G₅), -hexaose (G₆), -heptaose (G₇), -octaose (G₈), and amyloses ( and ), 113: 113: 113: 106: 113: 100: 106: 106. The Km values for N, K, I, ?M and SS were 2.4 mm, 0.58 mm, 20 mm, 1.6 mm and 5.0 mg/ml, respectively; those for G₂, G₃, G₄, G₅, G₆, G₇, G₈, and , 2.4 mm, 2.2 mm, 2.1 mm, 1.5 mm, 1.0 mm, 1.1 mm, 0.95 mm, 1.5 mm and 1.1 mm.

Rice α-glucosidase II is considered an enzyme with a preferential activity on maltooligosaccharides.     

On the Fermenting Ability of Sand Cultures of Acetone-Butanol Organisms Stored for Long Years

β-N-Acetyl-D-hexosaminidase was isolated from the mid-gut gland of Patinopecten yessoensis. The enzyme was purifted by making an acetone-dried preparation of the mid-gut gland, extracting with 50 mM citrate-phosphate buffer (pH 4.0) (about 13% of the extracted proteins was β-N-acetyl-D-hexosaminidase), ammonium sulfate fractionation, and column chromatographies on CM-Sepharose and DEAE-Sepharose. The purifted β-N-acetyl-D-hexosaminidase was homogeneous on SDS–PAGE, and sufficiently free from other exo-type glycosidases. The molecular weight was 56,000 by SDS–PAGE. The enzyme hydrolyzed both p-nitrophenyl β-N-acetyl-D-glucosaminide and p-nitrophenyl β-N-acetyl-D-galactosaminide. For p-nitrophenyl β-N-acetyl-D-glucosaminide, the pH optimum was 3.7, the optimum temperature was 45°C, and the K_m was 0.24 mM. For p-nitrophenyl β-N-acetyl-D-galactosaminide, these were pH 3.4, 45°C, and 0.15 mM, respectively. The enzyme liberated non-reducing terminal β-Iinked N-acetyl-D-glucosamine or N-acetyl-D-galactosamine from various 2-aminopyridyl derivatives of oligosaccharides of N-glycan or glycolipid type except of G_M2-tetrasaccharide. As the enzyme was stable around pH 3.5–5.5, it may be useful for long time reactions around the optimum pH.     

Biosynthetic Threonine Deaminase from Proteus morganii

Biosynthetic threonine deaminase was purified to an apparent homogeneous state from the cell extract of Proteus morganii, with an overall yield of 7.5%. The enzyme had a s⁰_20,w of 10.0 S, and the molecular weight was calculated to be approximately, 228,000. The molecular weight of a subunit of the enzyme was estimated to be 58,000 by sodium dodecyl sulfate gel electrophoresis. The enzyme seemed to have a tetrameric structure consisting of identical subunits. The enzyme had a marked yellow color with an absorption maximum at 415 nm and contained 2 mol of pyridoxal 5′-phosphate per mol. The threonine deaminase catalyzed the deamination of l-threonine, l-serine, l-cysteine and β-chloro-l-alanine. Km values for l-threonine and l-serine were 3.2 and 7.1 mm, respectively. The enzyme was not activated by AMP, ADP and ATP, but was inhibited by l-isoleucine. The Ki for l-isoleucine was 1.17 mm, and the inhibition was not recovered by l-valine. Treatment with mercuric chloride effectively protected the enzyme from inhibition by l-isoleucine.     

Synergistic Antimicrobial Effect of Acetic Acid,Sodium Chloride and Essential Oil Components

Acetic acid, NaCl and essential oil components were examined for their synergistic antimicrobial effect, using air-borne microorganisms and purely cultured fungi. Antimicrobial assays were carried out at 27°C, using 2% glucose Sabouraud agar. In order to completely suppress the growth of all the contaminating air microorganisms over a period of one month, more than 0.2% acetic acid or more than 25% NaCl was required in the medium. Any one of the essential oil components examined, at a concentration of as high as 1 mm or more, permitted considerable growth of various air microorganisms within several days after contamination. However, in combination with both 0.1% acetic acid and 3% NaCl, perillaldehyde, citral (αβ-unsaturated aliphatic aldehydes), citronellol, geraniol, perillalcohol (primary alcohols) or cuminaldehyde, at a concentration of 0.5 mm, completely suppressed the growth of all the contaminating air microorganisms over a period of one month.

Cinnamaldehyde was approximately twice as potent as these compounds in this respect, l-Menthol (secondary alcohol) and d-carvone (α,β-unsaturated ketone), at a concentration of 1 mm but not 0.5 mm, completely suppressed such microbial growth under the same exprimental conditions. Citronellal (α,β-saturated aldehyde) and linalool (tertiary alcohol) were somewhat less effective than l-menthol and d-carvone. Hydrocarbons examined (d-limonene, α-pinene, α-pinene, camphene, β-myrcene, β-caryophyllene and p-cymene), even at 2 mm, were only moderately effective in this respect.

Similar synergistic antimicrobial effects of these substances were observed when using purely cultured fungi.

These results strongly suggest that acetic acid, NaCl and certain essential oils (or their components), when combined together, are applicable at relatively lower concentrations for effective preservation of certain foods without applying synthetic preservatives.     

Studies on the Chemical Structure of Konjac Mannan

The electrophoretically homogeneous glucomannan isolated from konjac flour was composed of d-glucose and d-mannose residues in the approximate ratio of 1: 1.6. Controlled acid hydrolysis gave 4-O-β-d-mannopyranosyl-d-mannose, 4-O-β-d-mannopyranosyl-d-glucose_T 4-O-β-d-glucopyranosyl-d-glucose(cellobiose), 4-O-β-d-glucopyranosyl-d-mannose(epicellobiose), O-β-d-mannopyranosyl-(1→4)-O-β-d-mannopyranosyl-(1→4)-d-mannose, O-β-d-glucopyranosyl- (1→4)-O-β-d-mannopyranosyl-(1→4)-d-mannose, O-β-d-mannopyranosyl-(1→4)-O-β-d-glucopy- ranosyl-(1→4)-d-mannose and O-β-d-glucopyranosyl-(1→4)-O-β-d-glucopyranosyl-(1→4)-d-mannose.     

Enzyme-Substrate Complex of p-Hydroxybenzoate Hydroxylase; One of the Activated Intermediates of the Overall Reaction

The transglucosidation reaction of brewer’s yeast α-glucosidase was examined under the co-existence of l-sorbose and phenyl-α-glucoside. As the transglucosidation products, three kinds of new disaccharide were chromatographically isolated. It was presumed that these disaccharides consisting of d-glucose and l-sorbose were 1-O-α-d-glucopyranosyl-l-sorbose ([α]_D+89.0), 3-O-α-d-glucopyranosyl-l-sorbose ([α]_D+69.1) and 4-O-α-d-glucopyranosyl-l-sorbose ([α]_D+81.0). The principal product formed in the enzyme reaction was 1-O-α-d-glucopyranosyl-l-sorbose.     

Glycosidase-catalyzed Deoxy Oligosaccharide Synthesis. Practical Synthesis of Monodeoxy Analogs of Ethyl β-Thioisomaltoside Using Aspergillus niger α-Glucosidase

Enzymatic transglycosylation using four possible monodeoxy analogs of p-nitrophenyl α-D-glucopyranoside (Glcα-O-pNP), modified at the C-2, C-3, C-4, and C-6 positions (2D-, 3D-, 4D-, and 6D-Glcα-O-pNP, respectively), as glycosyl donors and six equivalents of ethyl β-D-thioglucopyranoside (Glcβ-S-Et) as a glycosyl acceptor, to yield the monodeoxy derivatives of glucooligosaccharides were done. The reaction was catalyzed using purified Aspergillus niger α-glucosidase in a mixture of 50 mM sodium acetate buffer (pH 4.0)/CH₃CN (1: 1 v/v) at 37°C. High activity of the enzyme was observed in the reaction between 2D-Glcα-O-pNP and Glcβ-S-Et to afford the monodeoxy analogs of ethyl β-thiomaltoside and ethyl β-thioisomaltoside that contain a 2-deoxy α-D-glucopyranose moiety at their glycon portions, namely ethyl 2-deoxy-α-D-arabino-hexopyranosyl-(1,4)-β-D-thioglucopyranoside and ethyl 2-deoxy-α-D-arabino-hexopyranosyl-(1,6)-β-D-thioglucopyranoside, in 6.72% and 46.6% isolated yields (based on 2D-Glcα-O-pNP), respectively. Moreover, from 3D-Glcα-O-pNP and Glcβ-S-Et, the enzyme also catalyzed the synthesis of the 3-deoxy analog of ethyl β-thioisomaltoside that was modified at the glycon α-D-glucopyranose moiety, namely ethyl 3-deoxy-α-D-ribo-hexopyranosyl-(1,6)-β-D-thioglucopyranoside, in 23.0% isolated yield (based on 3D-Glcα-O-pNP). Products were not obtained from the enzymatic reactions between 4D- or 6D-Glcα-O-pNP and Glcβ-S-Et.     

Synthesis of Certain Disaccharides Containing a α-or β- Rhamnopyranosidic Group and the Substrate Specificity of α-l-Rhamnosidase from Aspergillus niger

To investigate the substrate specificity of α-l-rhamnosidase from Aspergillus niger, the following seven substrates were synthesized: methyl 3-O-α-l-rhamnopyranosyl-α-d-mannopyranoside (1), methyl 3-O-α-l-rhamnopyranosyl-α-l-xylopyranoside (2), methyl 3-0-α-l-rhamnopyranosyl-α-l-rhamnopyranoside (3), methyl 4-0-α-l-rhamnopyranosyl-α-d-galactopyranoside (4), methyl 4-O-α-l-rhamnopyranosyl-α-d-mannopyranoside (5), methyl 4-0-α-l-rhamnopyra-nosyl-α-d-xylopyranoside (6), and 6-0-β-l-rhamnopyranosyl-d-mannopyranose (7). Compounds 1~6 were well-hydrolyzed by the crude enzyme, but 7 was unaffected.     

Regulatory Properties of Chorismate Mutase from Corynebacterium glutamicum

Regulatory properties of chorismate mutase from Corynebacterium glutamicum were studied using the dialyzed cell-free extract. The enzyme activity was strongly feedback inhibited by l-phenylalanine (90% inhibition at 0.1~1 mm) and almost completely by a pair of l-tyrosine and l-phenylalanine (each at 0.1~1 mm). The enzyme from phenylalanine auxotrophs was scarcely inhibited by l-tyrosine alone but the enzyme from a wild-type strain or a tyrosine auxotroph was weakly inhibited by l-tyrosine alone (40~50% inhibition, l-tyrosine at 1 mm). The enzyme activity was stimulated by l-tryptophan and the inhibition by l-phenylalanine alone or in the simultaneous presence of l-tyrosine was reversed by l-tryptophan. The Km value of the reaction for chorismate was 2.9 } 10^?3 m. Formation of chorismate mutase was repressed by l-phenylalanine. A phenylalanine auxotrophic l-tyrosine producer, C. glutamicum 98–Tx–71, which is resistant to 3-amino-tyrosine, p-aminophenylanaine, p-fluorophenylalanine and tyrosine hydroxamate had chorismate mutase derepressed to two-fold level of the parent KY 10233. The enzyme in C. glutamicum seems to have two physiological roles; one is the control of the metabolic flow to l-phenylalanine and l-tyrosine biosynthesis and the other is the balanced partition of chorismate between l-phenylalanine-l-tyrosine biosynthesis and l-tryptophan biosynthesis.