Polyamine synthesis in mammalian tissues. Isolation and characterization of spermidine synthase from bovine brain.

Spermidine synthase (EC 2.5.1.16) was purified to apparent homogeneity (about 11 000-fold) from bovine brain by affinity chromatography, with S-adenosyl-(5')-3-thiopropylamine linked to Sepharose as the adsorbent. The enzyme preparation was free from S-adenosylmethionine decarboxylase (EC 4.1.1.50) and spermine synthase (EC 2.5.1.22) activities. The native enzyme had an apparent Mr of 70 000, was composed of two subunits of equal size, and had an isoelectric point at pH 5.22. The apparent Km values for putrescine and decarboxylated adenosylmethionine [S-adenosyl-(5')-3-methylthiopropylamine] were 40 microM and 0.3 microM respectively. Cadaverine and 1,6-diaminohexane could replace putrescine as the aminopropyl acceptor, although the reaction rates were only 6% and 1% respectively of that obtained with putrescine. Ethyl, propyl and carboxymethyl analogues of decarboxy-S-adenosylmethionine could act as propylamine donors. Both the reaction products, spermidine and 5'-methylthioadenosine, were mixed-type inhibitors of the enzyme. On the basis of initial-velocity and product-inhibition studies, a ping-pong reaction mechanism for the spermidine synthase reaction was ruled out.     

Polyamine synthesis in mammalian tissues. Isolation and characterization of spermine synthase from bovine brain

Spermine synthase, a propylamine transferase, which catalyses the biosynthesis of spermine from S-methyladenosylhomocystemine and spermidine has been purified to an apparent homogeneity (about 6000-fold) from bovine brain using spermine-Sepharose affinity chromatography. The enzyme preparation was free from S-adenosylmethionine decarboxylase and spermidine synthase activities. The molecular Stokes radius of the enzyme was calculated to be 4.16 nm. The enzyme has an apparent molecular weight of approximately 88 000, composing of two subunits of equal size. The enzyme showed a broad pH optimum between 7.0 and 8.0 and an acidic isoelectric point at pH 5.10. The apparent Km values for S-methyladenosylhomocysteamine was 0.6 microM and about 60 microM for spermidine. The enzyme showed strict specificity to spermidine as the propylamine acceptor. Both the reaction products, spermine and 5'-methylthioadenosine inhibited the enzyme activity, methylthioadenosine being a powerful competitive inhibitor with respect to S-methyladenosylhomocysteamine (Ki value of about 0.3 microM). Putrescine also inhibited competitively with respect to spermidine (Ki value of about 1.7 mM). Spermine synthase had no requirements for metal or other cofactors.     

Purification and partial characterization of 7,8-dihydro-6-hydroxymethylpterin-pyrophosphokinase and 7,8-dihydropteroate synthase from Escherichia coli MC4100.

The enzymes 7,8-dihydroxymethylpterin-pyrophosphokinase (HPPK) and 7,8-dihydropteroate synthase (DHPS), which act sequentially in the folate pathway, were purified to homogeneity from crude extracts of Escherichia coli MC4100. The enzymes represent less than 0.01% of the total soluble protein. HPPK was purified greater than 10,000-fold; the native enzyme appears to be a monomer with a molecular mass of 25 kDa and a pI of 5.2. DHPS was purified greater than 7,000-fold; the native enzyme has an apparent molecular mass of 52 to 54 kDa and is composed of two identical 30-kDa subunits. The amino-terminal sequences for both enzymes have been determined.     

Purification of hepoxilin epoxide hydrolase from rat liver

Hepoxilin epoxide hydrolase activity was demonstrated in rat liver cytosol using as substrate [1-14C] hepoxilin A3, a recently described hydroxy epoxide derivative of arachidonic acid. The enzyme was isolated and purified to apparent homogeneity using conventional chromatographic procedures resulting in 41-fold purification. The protein eluted during isoelectric focusing at a pI in the 5.3-5.4 range. The specific activity of the purified protein was 1.2 ng/microgram protein/20 min at 37 degrees C. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under denaturing conditions, a molecular mass value of 53 kDa was observed. Using native polyacrylamide gel electrophoresis, enzyme activity corresponded to the main protein band. The purified protein used hepoxilin A3 as preferred substrate converting it to trioxilin A3. The enzyme was marginally active toward other epoxides such as leukotriene A4 and styrene oxide. The Mr, pI, and substrate specificity of the hepoxilin epoxide hydrolase indicate that this enzyme is different from the recently reported leukotriene A4 hydrolase from human erythrocytes and rat and human neutrophils and constitutes a hitherto undescribed form of epoxide hydrolase with specificity toward hepoxilin A3. Tissue screening for enzyme activity revealed that this enzyme is ubiquitous in the rat.     

Isolation and purification of chloroplastic spinach (Spinacia oleracea) sedoheptulose-1,7-bisphosphatase.

Higher-plant sedoheptulose-1,7-bisphosphatase was isolated and purified over 200-fold from spinach (Spinacia oleracea) chloroplast stromal extracts to apparent electrophoretic homogeneity by DEAE-Fractogel, molecular sieving on Sephadex G-200 and Blue B dye-matrix affinity chromatography. It is a protein of Mr 66,000, made up of two apparently identical subunits (Mr 35,000). The enzyme is activated by reduced thioredoxin fb in the presence of dithiothreitol. Its specificity towards sedoheptulose 1,7-bisphosphate versus fructose 1,6-bisphosphate is high, but not absolute.     

Characterization of tyrosine hydroxylase from bovine adrenal medulla

Tyrosine hydroxylase purified to apparent homogeneity from the soluble fraction of bovine adrenal medulla had an apparent Mr of about 280,000 by Bio-Gel A-1.5m chromatography, and gave a single band with a Mr of 60,000 by sodium dodesyl sulfate polyacrylamide gel electrophoresis. The enzyme is considered to be composed of four identical subunits. Isoelectric point of purified enzyme was pH 6.0. The amino acid composition of the enzyme was characterized by fairly high contents of glutamic acid and alanine residues. The N-terminal amino acid was determined to be glutamic acid.     

Human skin tryptase: purification, partial characterization and comparison with human lung tryptase

Human skin tryptase was isolated using stepwise low- and high-salt extraction and further purified 448-fold with 33% yield using octyl-Sepharose CL-4B hydrophobic affinity chromatography, Sephacryl S-200 gel filtration and finally octyl-Sepharose CL-4B or cellulose phosphate ion exchange chromatography. The skin tryptase, which has an apparent Mr of 120,000 by gel filtration in high-salt buffer, consisted of polypeptide chains of Mr 34,000 and 38,000 when resolved on SDS gels. Both polypeptide chains, labelled with [3H]diisopropyl fluorophosphate, indicated that they were representative of subunits and that the native proteinase was an aggregate of subunits. However, in some preparations only one band with Mr 34,000 was seen. In low-salt buffer the enzyme was labile and at least 1.4 M KCl was needed to keep the enzyme stabile when incubated at 37 degrees C for 30 min. Heparin glycosaminoglycan partially stabilized the tryptase but addition of protein (e.g. albumin, 80 micrograms/ml) to the tryptase-heparin mixture was needed to keep the enzyme stabile. Tryptases purified by exactly the same method from human lung tissue and from human skin had identical molecular size in gel filtration and in SDS-polyacrylamide gel electrophoresis. They also revealed identical enzyme kinetic parameters with several synthetic peptide substrates. The inhibition profile was identical for both enzymes, and they also crossreacted completely in immunodiffusion plates. These studies strongly indicate that mast cells found in skin as well as lung contain closely related, possible identical trypsin-like proteinases.     

Purification and characterization of 1-aminocyclopropane-1-carboxylate synthase from etiolated mung bean hypocotyls

1-Aminocyclopropane-1-carboxylate (ACC) synthase, EC 4.4.1.14, was purified to homogeneity from etiolated mung bean hypocotyl segments. This was made possible by the ability to elevate the enzyme level markedly through hormone treatments and by stabilization of the enzyme with high phosphate concentrations. The four-step procedure resulted in 1050-fold purification with 25% yield, and consisted of stepwise elution from hydroxylapatite, chromatography on phenyl-Sepharose CL-4B, gradient elution from hydroxylapatite, and fast protein liquid chromatography (FPLC) on a MonoQ anion-exchange column. FPLC-purified ACC synthase migrated as a single band of Mr 65,000 on denaturing polyacrylamide gel electrophoresis. The molecular weight of native enzyme by Bio-Gel A-0.5 M chromatography was 125,000, indicating that the enzyme probably exists as a dimer of identical 65,000 Mr subunits. The mung bean ACC synthase exhibited a pH optimum of 8.0 for activity and a Km for S-adenosylmethionine (AdoMet) of 55 microM at 30 degrees C. It exhibited an Arrhenius activation energy of 12 kcal mol-1 degree-1 and was inactivated at temperatures in excess of 40 degrees C. The specific activity for pure ACC synthase was 21 mumol of ACC formed/mg protein/h when determined under optimal conditions with 400 microM AdoMet.     

Purification and properties of a protamine kinase and a type II casein kinase from bovine kidney mitochondria

Bovine kidney mitochondrial extracts contain an inactive protamine kinase and an inactive casein kinase. The protamine kinase was activated by chromatography on poly(L-lysine)-agarose. Two forms of this soluble mitochondrial protamine kinase were separated by chromatography on protamine-agarose. Both forms were purified about 80,000-fold to apparent homogeneity. Both forms of the protamine kinase consist of a single polypeptide chain with an apparent Mr approximately 45,000. Both enzyme forms underwent autophosphorylation without significant effect on activity, and both forms exhibited identical substrate specificities. The protamine kinase showed little activity toward branched-chain alpha-keto acid dehydrogenase (less than 3%), and it was essentially inactive (less than 0.1%) with pyruvate dehydrogenase, casein, and ovalbumin. The enzyme was active with histone H1 and with bovine serum albumin. Protamine kinase activity was unaffected by heparin (up to 100 micrograms/ml), by the protein inhibitor of cyclic AMP-dependent protein kinase, by Ca2+ and calmodulin, and by monoclonal antibody to the catalytic domain of protein kinase C from rat brain. The casein kinase was activated in the presence of spermine or by chromatography of the extract on DEAE-cellulose or poly(L-lysine)-agarose. The enzyme was purified about 80,000-fold to apparent homogeneity. It exhibited an apparent Mr 130,000 as determined by gel-permeation chromatography on Sephacryl S-300 in the presence of 0.5 M NaCl. Two subunits, with apparent Mr's 36,000 (alpha) and 28,000 (beta) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The kinase underwent autophosphorylation of its beta-subunit, without significant effect on activity. Casein kinase activity was inhibited 50% by 1.5 micrograms/ml of heparin. Spermine (1.0 mM) stimulated activity of the purified kinase two- to three-fold at 1.5 mM Mg2+. Half-maximal stimulation occurred at 0.1 mM spermine. The kinase utilized both ATP and GTP as substrates. The casein kinase showed little activity (less than 1%) toward pyruvate dehydrogenase and branched-chain alpha-keto acid dehydrogenase from kidney mitochondria, and the kinase was essentially inactive with glycogen synthase a. The properties of this soluble mitochondrial kinase indicate that it is a type II casein kinase.     

Potato tuber succinate semialdehyde dehydrogenase: purification and characterization

Succinate semialdehyde dehydrogenase (SSADH) has been purified from potato tubers with 39% yield, 832-fold purification, and a specific activity of 6.5 units/mg protein. The final preparation was homogeneous as judged from native and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel filtration on Sepharose 6B gave a relative molecular mass (Mr) of 145,000 for the native enzyme. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave a single polypeptide band of Mr 35,000. Thus the enzyme appears to be a tetramer of identical subunits. Chromatofocusing of the enzyme gave a pI of 8.7. The enzyme was maximally active at pH 9.0 in 100 mM sodium pyrophosphate buffer. In 100 mM Tris-HCl buffer, pH 9.0, the enzyme gave only 20% of the activity found in pyrophosphate buffer and had a shorter linear rate. The enzyme was specific for succinate semialdehyde (SSA) as substrate and could not utilize acetaldehyde, glyceraldehyde 3-phosphate, malonaldehyde, lactate, or ethanol as substrates. The enzyme was also specific for NAD+ as cofactor and NADP+ and 3-acetylpyridine adenine dinucleotide could not serve as cofactors. Potato SSADH had a Km of 4.6 microM for SSA when assayed in pyrophosphate buffer and was inhibited by that substrate at concentrations greater than 120 microM. The Km for NAD+ was found to be 31 microM. The enzyme required exogenous addition of a thiol compound for maximal activity and was inhibited by the thiol-directed reagents p-hydroxymercuribenzoate, dithionitrobenzoate, and N-ethyl-maleimide, by heavy metal ions Hg2+, Cu2+, Cd2+, and Zn2+, and by arsenite. These results indicate a requirement of a SH group for catalytic activity.     

N5-(L-1-carboxyethyl)-L-ornithine:NADP+ oxidoreductase from Streptococcus lactis. Purification and partial characterization

N5-(L-1-Carboxyethyl)-L-ornithine:NADP+ oxidoreductase (EC 1.5.1.-) from Streptococcus lactis K1 has been purified 8,000-fold to homogeneity. The NADPH-dependent enzyme mediates the reductive condensation between pyruvic acid and the delta- or epsilon-amino groups of L-ornithine and L-lysine to form N5-(L-1-carboxyethyl)-L-ornithine and N6-(L-1-carboxyethyl)-L-lysine, respectively. The five-step purification procedure involves ion-exchange (DE52 and phosphocellulose P-11), gel filtration (Ultrogel AcA 44), and affinity chromatography (2',5'-ADP-Sepharose 4B). Approximately 100-200 micrograms of purified enzyme of specific activity 40 units/mg were obtained from 60 g of cells, wet weight. Anionic polyacrylamide gel electrophoresis revealed a single enzymatically active protein band, whereas three species (pI 4.8-5.1) were detected by analytical electrofocusing. The purified enzyme is active over a broad pH range of 6.5-9.0 and is stable to heating at 50 degrees C for 10 min. Substrate Km values were determined to be: NADPH, 6.6 microM; pyruvate, 150 microM; ornithine, 3.3 mM; and lysine, 18.2 mM. The oxidoreductase has a relative molecular mass (Mr = 150,000) as estimated by high pressure liquid chromatography exclusion chromatography and by polyacrylamide gradient gel electrophoresis. Conventional gel filtration indicated an Mr = 78,000, and a single protein band of Mr = 38,000 was revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme is composed of identical subunits of Mr = 38,000, which may associate to yield both dimeric and tetrameric forms. Polyclonal antibody to the purified protein inhibited enzyme activity. The amino acid composition of the enzyme is reported, and the sequence of the first 37 amino acids from the NH2 terminus has been determined by stepwise Edman degradation.     

Purification and some properties of a novel heat-stable cis-toluene dihydrodiol dehydrogenase.

cis-Toluene dihydrodiol dehydrogenase was purified 200-fold from cells of a thermotolerant Bacillus species grown with toluene as the sole source of carbon and energy. The purified enzyme preparation was remarkably heat-stable and exhibited a half-life of 100 min at 80 degrees C, the temperature optimum. The activation energy of the reaction was 36 kJ.mol-1. Isoelectric focusing indicated that the pI of the native enzyme was 6.4 and that of the denatured enzyme 6.5. Although the pH optimum was 9.8, the enzyme was most stable at pH 8. The Mr of the enzyme was approx. 172,000 as determined by gel filtration and 166,000 by polyacrylamide-gel electrophoresis. The enzyme was composed of six apparently identical subunits with Mr values of 29,500. Kinetic analysis revealed that the Km for cis-toluene dihydrodiol was 92 microM and for NAD+ was 80 microM. The apparent Km values for cis-benzene dihydrodiol and cis-naphthalene dihydrodiol were 330 microM and 51 microM respectively. The enzyme was inhibited by mercurials but was unaffected by metal-ion chelators. Steady-state kinetics and product-inhibition patterns suggested that the enzyme mechanism was ordered Bi Bi.     

Purification and characterization of thymidylate synthetase from rat regenerating liver

Thymidylate synthetase (EC 2.1.1.45) from rat regenerating liver has been purified over 5000-fold to apparent homogeneity by a procedure involving two affinity methods. Molecular weight of the native enzyme was found to be about 68,000, as determined by gel filtration. Electrophoresis in polyacrylamide gels containing sodium dodecyl sulfate yielded a single band of molecular weight of 35,000, suggesting that thymidylate synthetase is a dimer of very similar or identical subunits. The Michaelis constants for deoxyuridylate (dUMP) and (+/-)L-5,10-methylenetetrahydrofolate are 6.8 microM and 65 microM, respectively. Reaction kinetics and product inhibition studies reveal the enzymatic mechanism to be ordered sequential. 5-Fluoro-dUMP, halogenated analog of the nucleotide substrate is a competitive inhibitor of the enzyme, with an apparent Ki value of 5 nM. Amethopterin, analog of the cofactor is also a competitive inhibitor with an apparent Ki value of 23 microM.     

Affinity-chromatographic purification of S-adenosyl-L-homocysteine hydrolase. Some properties of the enzyme from rat liver.

S-Adenosyl-L-homocysteine hydrolase has been purified to apparent homogeneity from rat liver by means of affinity chromatography on 8-(3-aminopropylamino)adenosine linked to Sepharose. The purified enzyme was free from adenosine kinase and adenosine deaminase activities and was homogeneous on SDS/polyacrylamide-gel electrophoresis which gave a subunit mol.wt. of 47 000. The native enzyme showed some microheterogeneity on polyacrylamide-gel electrophoresis under increased-resolution conditions but was homogeneous on isoelectric focusing (pI 5.6). The molecular weight of the native enzyme was about 220 000 as judged by pore-gradient electrophoresis. The native enzyme bound adenosine tightly and showed Km values of 0.6 microM, 0.9 microM and 60 microM for adenosine, S-adenosyl-L-homocysteine and L-homocysteine respectively. The enzyme was rapidly inactivated when incubated in the presence of adenosine, S-adenosyl-L-homocysteine or several adenosine derivatives or analogues. Inactivation took place both at 0 and 37 degrees C. Freezing in the absence of glycerol resulted in the appearance of dissociation products of the oligomeric protein. Multimer formation was observed at low thiol concentrations.     

One-step purification and properties of catalase from leaves of Zantedeschia aethiopica

Catalase (E.C 1.11.1.6) was purified from leaves of Zandedeschia aethiopica to apparent homogeneity by a one-step hydrophobic interaction chromatography on a phenyl Sepharose CL-4B column. The purified enzyme preparation was obtained with a final recovery of enzyme activity of about 61% and a specific activity of 146 U/mg protein. The purified enzyme ran as a single protein band when analyzed both by native PAGE and SDS-PAGE corresponding to an Mr of 220,000 Da, which consists of 4 subunits with identical Mr of 54,000 Da. The pI of purified enzyme was found to be 5.2 by isoelectric focusing on ultrathin polyacrylamide gels. The purified catalase has an optimum temperature of activity at 40 degrees C, whereas it is stable between 0 degrees and 50 degrees C. As regards pH, the enzyme has an optimum activity at pH 7.0 and it is stable in the range pH 6-8. The absorption spectrum of the purified enzyme exhibited 2 peaks at 280 nm and 405 nm.     

Microbial metabolism of quinoline and related compounds. XII. Isolation and characterization of the quinoline oxidoreductase from Rhodococcus spec. B1 compared with the quinoline oxidoreductase from Pseudomonas putida 86.

Quinoline oxidoreductase from Rhodococcus spec. B1 was purified 39-fold to apparent homogeneity in a 5-step procedure with a recovery of 26%. The Mr of the native enzyme as determined by gel chromatography was 300,000. SDS polyacrylamide gel electrophoresis of the enzyme revealed 3 protein bands corresponding to Mr 82,000, 32,000, and 18,000. The enzyme contains 1.3 atoms of molybdenum, 8 atoms of iron, 8 atoms of acid-labile sulphur, 2 molecules of FAD and 2 molecules of molybdopterin cytosine dinucleotide. Cyanide, 4-hydroxymercuribenzoate and methanol were effective as inhibitors. The amino-terminal protein sequences of the 3 subunits of quinoline oxidoreductase from Rhodococcus B1 compared to those of quinoline oxidoreductase from Pseudomonas putida 86 revealed no difference among 71 amino acids examined.     

Purification and properties of the 5,10-methenyltetrahydromethanopterin cyclohydrolase from Methanobacterium thermoautotrophicum.

The 5,10-methenyltetrahydromethanopterin cyclohydrolase of Methanobacterium thermoautotrophicum was purified 128-fold to homogeneity. The enzyme had a subunit Mr of 41,000 as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. From high-performance size exclusion chromatography of the native protein, an Mr of 82,000 was determined, suggesting a dimer of identical subunits. The enzyme was inhibited by 10-formyltetrahydromethanopterin and stimulated by Mg2+. Evaluation of the reaction equilibrium indicated that the methenyl derivative was favored over 5-formyltetrahydromethanopterin, with a much higher equilibrium constant than for the analogous reaction of tetrahydrofolate derivatives. Folate derivatives did not serve as substrates for this enzyme.     

Characterization of human spermidine/spermine N1-acetyltransferase purified from cultured melanoma cells

Extreme inducibility of spermidine/spermine acetyltransferase (SSAT) by bis-ethyl derivatives of spermine in human large cell lung carcinoma and melanoma cells has prompted biochemical characterization of the purified enzyme. Treatment of human MALME-3 melanoma cells with 10 microM N1,N11-bis(ethyl)norspermine (BENSPM) for 48-72 h increased SSAT activity by some 1000- to 4000-fold and enabled purification of the enzyme by established procedures--binding on immobilized spermine and elution with spermine followed by binding on Matrex Blue A and elution with coenzyme A. The enzyme showed a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a single subunit species and molecular weight of approximately 20,300 Da. By gel permeation chromatography, the holoenzyme was found to have a molecular weight of 80,000 Da, suggesting a total of four identical subunits. Purified SSAT had a specific activity of 285 mumol/min/mg for spermidine and Km values of 5.9 microM for acetylcoenzyme A, 55 microM for spermidine, 5 microM for spermine, 36 microM for N1-acetylspermine, 1.6 microM for norspermidine, and 4 microM for norspermine. Homologs of BENSPM were found to be competitive inhibitors of spermidine acetylation, with Ki values of 0.8 microM for BENSPM, 1.9 microM for N1,N12-bis-(ethyl)spermine and 17 microM for N1,N14-bis-(ethyl)-homospermine. Correlation of these values with the relative abilities of the homologs to increase SSAT in intact cells suggests that formation of an enzyme inhibitor complex may play a contributing role in enzyme induction.     

Flavanone synthase from Petroselinum hortense. Molecular weight, subunit composition, size of messenger RNA, and absence of pantetheinyl residue.

Flavanone synthase from irradiated cell suspension cultures of parsley was purified to apparent homogeneity. Molecular weights of about 77 000 for the enzyme and about 42 000 for the subunits were determined respectively by sedimentation-equilibrium measurements and disc-gel electrophoresis in the presence of dodecyl sulfate. A specific antiserum was prepared for the enzyme and was used in an assay for flavanone synthase mRNA activity in partially purified RNA preparations. The apparent molecular size of flavanone synthase mRNA was estimated by sucrose gradient centrifugation and gel electrophoresis under partially denaturing conditions. Values of about 17 S and Mr = 0.62 X 10(6) were obtained. The fractionation patterns suggested that flavanone synthase mRNA was homogeneous in size. All together, the results support the idea that the enzyme is composed of two subunits which are probably identical. Amino acid analysis and a microbial assay were carried out to test the possible occurrence of cysteamine, beta-alanine, and pantothenate in the enzyme. The results were negative, indicating the absence of pantetheine or a similar residue. The possible similarity in mechanism between flavanone synthase and 3-oxoacyl-(acyl carrier protein) synthase is discussed.     

Arogenate dehydrogenase from Streptomyces phaeochromogenes. Purification and properties

Arogenate dehydrogenase, the terminal enzyme of tyrosine biosynthesis in Streptomyces phaeochromogenes, was purified to homogeneity by a five-step procedure. The enzyme is a dimer of Mr 57 600 as determined by dodecyl sulfate polyacrylamide gel electrophoresis after cross-linking of the monomers, or of 66 300 as found by gel permeation chromatography, and consists of two identical subunits of Mr 28 100. The pI of the enzyme is 4.45, and the Km values are 0.105mM for arogenate and 0.01 mM for NAD.