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PubMed1994

Cloning and expression of pigeon liver cytosolic NADP(+)-dependent malic enzyme cDNA and some of its abortive mutants.

A full-length 1927-base-pair cDNA of pigeon liver malic enzyme was obtained by utilizing the screening of the cDNA library and polymerase chain reaction techniques. The cDNA contained one open reading frame coding for 557 amino acid residues, flanked by 86 and 167 nucleotides at the 5' and 3' termini, respectively, and was successfully cloned and expressed in Escherichia coli cells. Functionally active recombinant malic enzyme was purified from the cells. This recombinant enzyme has a Km value for L-malate of 160 +/- 30 microM, which is almost identical to that for the natural enzyme (150 +/- 17 microM). The Km value for Mn2+ (4.2 +/- 0.3 microM) is higher than that for the natural pigeon malic enzyme (1.4 +/- 0.2 microM), while the Km value for NADP+ (3.8 +/- 0.3 microM) is lower than that for the natural enzyme (10.8 +/- 0.1 microM). The catalytic constant (kcat) for the recombinant enzyme is decreased by 3.6-fold, but the substrate inhibition constant for L-malate is increased by about 40-fold. Change in the quaternary structure of the recombinant enzyme was revealed in the pH perturbation examination. A truncated pigeon liver malic enzyme, lacking the first 13 amino acid residues, and a recombinant protein, mutated at F19S, N250S, and L353Q, showed no enzymatic activity. Both abortive recombinant mutant proteins were still able to bind with 2',5'-ADP agarose; however, the fluorescence emission spectrum of the protein bound NADPH did not show a blue shift as the natural enzyme. In accordance with these observations, we suggest that the adenosine 2',5'-bisphosphate binding domain of the NADP+ binding site in the beta alpha beta motif may still be retained in these mutant proteins. However, the local hydrophobic environment for the binding of the nicotinamide moiety of the coenzyme molecule may be altered. Therefore, the lack of catalytic activity of the mutant proteins could be attributed to an improper orientation of the bound NADP+.

Adenosine Diphosphate↗
PubMed1995

Purification and characterization of an acyclic monoterpene primary alcohol:NADP+ oxidoreductase from catmint (Nepeta racemosa).

A soluble monoterpene primary alcohol:NADP+ oxidoreductase has been purified to apparent homogeneity from leaves of the catmint, Nepeta racemosa. The purified enzyme consisted of two polypeptides, with molecular masses of 42,000 and 40,000 Da, and contained zinc ions. A number of monoterpene alcohols (geraniol, nerol, citronellol, and their hydroxylated derivatives) were substrates, but the enzyme was inactive toward ethanol. The enzyme required NADP(H) as cofactor, with NAD(H) ineffective. Gas chromatographic and coupled mass spectrometric analysis of the reaction products showed that 10-hydroxygeraniol and 10-hydroxynerol were oxidized by the enzyme in the presence of NADP+, at both C-1 and C-10. These results are consistent with a role for this enzyme in the biosynthesis of iridoid monoterpenes.

Alcohol Oxidoreductases↗
PubMed1992

An NADP(+)-dependent glycerol dehydrogenase in Aspergillus nidulans is inducible by D-galacturonate.

In Aspergillus nidulans there is an NADP(+)-dependent glycerol dehydrogenase that is specifically induced on transfer to D-galacturonate medium. In contrast to the previously characterised constitutive NADP(+)-dependent glycerol dehydrogenase it has a much broader substrate specificity, having activity as an ethanol dehydrogenase, and is subject to carbon-catabolite repression. In addition to the two NADP(+)-dependent glycerol dehydrogenases, alcohol dehydrogenase I and II are also present on transfer to D-galacturonate medium, and have weak activity as glycerol dehydrogenases.

Alcohol Dehydrogenase↗
PubMed1986

NAD kinase from Bacillus licheniformis: inhibition by NADP and other properties.

NAD kinase was purified 180-fold from Bacillus licheniformis to determine the role it plays in NADP turnover in this organism. The enzyme was found to have a pH optimum of 6.8 and an apparent Km for NAD of 2.7 mM. The ATP saturation curve was not hyperbolic; 5.5 mM ATP was required to reach half maximal activity. Both Mn2+ and Ca2+ could be substituted for Mg2+. Several compounds including nicotinic acid, nicotinamide, nicotinamide mononucleotide, quinolinic acid, NADPH, ADP, AMP and cyclic AMP did not affect NAD kinase activity. In contrast, the enzyme was inhibited by NADP at concentrations typically found in logarithmic cells of B. licheniformis. This inhibition was competitive with NAD and had a Ki of 0.13 mM. It is suggested that in vivo NAD kinase activity is highly dependent on the concentrations of NAD and ATP and the proportion of oxidized and reduced NADP.

Adenosine Triphosphate↗
PubMed1977

An NADP-linked acetoacetyl CoA reductase from Zoogloea ramigera.

Zoogloea ramigera I-16 M was found to contain two stereospecific acetoacetyl CoA reductases; one was NADP+-linked and D(-)-beta-hydroxybutyryl CoA specific and the other was NAD+-linked and L(+)-isomer specific. The NADP+-linked enzyme, purified approximately 150-fold, had a pH optimum for the reduction of acetoacetyl CoA at 8.1, but no definite pH optimum for the oxidation for beta-hydroxybutyryl CoA. The apparent Michaelis constants for acetoacetyl CoA and NADPH were 8.3 and 21 micrometer, respectively. The enzyme was markedly inhibited by acetoacetyl CoA at concentrations higher than 10 micrometer. The incorporation of [1-14C]acetyl CoA into poly-beta-hydroxybutyrate (PHB) by bacterial crude extract (containing beta-ketothiolase, acetoacetyl CoA reductases, enoyl CoA hydratases and PHB synthases) or by a system reconstituted from purified preparations of beta-ketothiolase, acetoacetyl CoA reductase and PHB synthase, was observed only in the presence of NADPH, but not NADH. Among various enzymes involved in PHB metabolism, only the specific activity of glucose 6-phosphate dehydrogenase was elevated 5-fold within 2 h after the addition of glucose to the cells grown in the basal medium. These findings suggest that, in Z. ramigera I-16M, acetoacetyl CoA is directly reduced to D(-)-beta-hydroxybutyryl CoA by the NADP+-dependent reductase, and PHB synthesis is at least partially controled by NADPH availability through glucose 6-phosphate dehydrogenase.

Acetoacetates↗
PubMed1985

Studies of the ferricyanide reductase activities of the mitochondrial reduced nicotinamide adenine dinucleotide-ubiquinone reductase (complex I) utilizing arylazido-beta-alanyl NAD+ and arylazido-beta-alanyl NADP+.

The NADH and NADPH ferricyanide reductase activities present in mitochondrial NADH-CoQ reductase preparations have been studied utilizing two photoaffinity pyridine nucleotide analogues: arylazido-beta-alanyl NAD+ (A3'-O-[3-[N-(4-azido-2-nitrophenyl)amino]propionyl]NAD+) and arylazido-beta-alanyl NADP+ (N3'-O-[3-[N-(4-azido-3-nitrophenyl)amino]propionyl]NADP+). For the NADH-K3Fe(CN)6 reductase activity, arylazido-beta-alanyl NAD+ was found to be, in the dark, a competitive inhibitor with respect to both NADH and K3Fe(CN)6 with Ki,app values of 9.7 and 15.5 microM, respectively. In comparison the NADP+ analogue exhibited weak noncompetitive inhibitor activity for this reaction against both substrates. Upon photoirradiation arylazido-beta-alanyl NAD+ inhibited NADH-K3Fe(CN)6 reductase up to 70% in the presence of a 25-fold molar excess of analogue over the enzyme concentration. This photodependent inhibition could be prevented by the presence, during irradiation, of the natural substrate NADH. In contrast complex kinetic results were obtained with studies of the effects of the pyridine nucleotide analogues of NADPH-K3Fe(CN)6 reductase activity in the dark. Photoirradiation of either analogue in the presence of the enzyme complex resulted in an activation of NADPH-dependent activity. The possibility that the NADPH-K3Fe(CN)6 reductase activity of complex I represents a summation of the combined ferricyanide reductase activity of the NADPH-NAD+ transhydrogenase and NADH oxidoreductase is suggested.

Animals↗
PubMed1999

The Aspergillus nidulans gltA gene encoding glutamate synthase is required for ammonium assimilation in the absence of NADP-glutamate dehydrogenase.

Mutants of Aspergillus nidulans lacking NADP-glutamate dehydrogenase activity grow more poorly than wild-type strains on ammonium as a sole nitrogen source. The leaky growth of these mutants is indicative of an alternative pathway of ammonium assimilation and glutamate biosynthesis. We have PCR-amplified a portion of the A. nidulans gene encoding glutamate synthase and used this sequence to inactivate the genomic copy. This gene, designated gltA, was found to be dispensable for growth on ammonium in the presence of NADP-glutamate dehydrogenase activity. However, a strain carrying the gltA inactivation together with an NADP-glutamate dehydrogenase structural gene mutation (gdhA) was unable to grow on ammonium or on nitrogen sources metabolized via ammonium. The gltA gene was located to linkage group V of the A. nidulans genetic map.

Amino Acid Sequence↗
PubMed1983

3-aminopyridine 1,N6-ethenoadenine dinucleotide phosphate: a fluorescent reagent for NADP-requiring enzymes.

3-Aminopyridine 1,N6-ethenoadenine dinucleotide phosphate (epsilon-AADP) was synthesized from 3-aminopyridine adenine dinucleotide phosphate by reaction with chloroacetaldehyde. The reaction was monitored by high-pressure liquid chromatography. The product, epsilon-AADP, was purified by ion-exchange chromatography followed by a Sephadex G-10 desalting process. Spectrophotometric and fluorimetric properties of epsilon-AADP were obtained at neutral pH. Diazotization of epsilon-AADP was documented by azodye formation at pH values below 3 and the diazotized derivative was shown to react rapidly with sulfhydryl compounds at neutrality. As an analog of NADP, epsilon-AADP was demonstrated to be an effective NADP-competitive inhibitor of NADP-requiring dehydrogenases, reductases, and an NAD glycohydrolase.

Adenine Nucleotides↗
PubMed1984

A rapid and convenient preparation of [4-3H]NADP and stereospecifically tritiated NADP3H.

The enzymatic preparation and chromatographic purification of [4-3H]NADP and NADPH stereospecifically labeled with 3H on either the A or B faces at position 4 have been simplified. Commercially available [1-3H]glucose was used as a starting material for the sequential synthesis of [4B-3H]NADPH, [4-3H]NADP, and [4A-3H]NADPH. These products were rapidly purified by step elution of DEAE-cellulose minicolumns so that [4B-3H]NADPH was produced and purified from [1-3H]glucose in 2 h, [4-3H]NADP in 5 h, and [4A-3H]NADPH in 8 h. Yields of these products were 65 to 88% starting with [1-3H]glucose. Analysis of the products by high-performance liquid chromatography indicated radiochemical purities of 82-95% for these compounds and specific activities equivalent to that of the starting material (10-15 Ci/mmol).

Chromatography, DEAE-Cellulose↗
PubMed1992

An enzymatic cycling procedure for beta-NADP+ generated by 3'-phosphodiesterase, 2':3'-cyclic nucleotide.

An enzymatic cycling procedure for beta-NADP+ generated by the enzyme 3'-phosphodiesterase, 2':3'-cyclic nucleotide (EC 3.1.4.37) from its substrate 2':3'-cyclic NADP+ is described. The enzymes glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and diaphorase (EC 1.8.1.4) are used to cycle the cofactor between its oxidized and reduced forms in the presence of glucose-6-phosphate and p-iodonitrotetrazolium violet (INT) with the concomitant production of colored INT-formazan, monitored at 492 nm. The amplification is about 400-fold per hour and is sensitive enough to detect 6 x 10(-13) mol of NADP(H). A simple procedure for the optimization of this cycling assay is also described. Conjugates to 3'-phosphodiesterase, 2':3'-cyclic nucleotide may be used in heterogeneous enzyme immunoassays for the detection of small quantities of haptens or proteins in biological fluids.

2',3'-Cyclic Nucleotide 3'-Phosphodiesterase↗
PubMed1988

Modification of NAD-dependent isocitrate dehydrogenase by the 2',3'-dialdehyde derivatives of NAD, NADH, NADP, and NADPH.

The 2',3'-dialdehyde nicotinamide ribose derivatives of NAD (oNAD) and NADH (oNADH) have been prepared enzymatically from the corresponding 2',3'-dialdehyde analogs of NADP and NADPH. Pig heart NAD-dependent isocitrate dehydrogenase requires NAD as coenzyme but binds NADPH, as well as NADH, ADP, and ATP, at regulatory sites. Incubation of 1-3 mM oNAD or oNADH with this isocitrate dehydrogenase causes a time-dependent decrease in activity to a limiting value 40% that of the initial enzyme, suggesting that reaction does not occur at the catalytic coenzyme site. Upon varying the concentration of oNAD or oNADH from 0.2 to 3 mM, the inactivation rate constants increase in a nonlinear manner, consistent with reversible binding of oNAD and oNADH to the enzyme prior to covalent reaction. Inactivation is accompanied by incorporation of radioactive reagent with extrapolation to 0.54 mol [14C]oNAD or 0.45 mol [14C]oNADH/mol average enzyme subunit (or about 2 mol reagent/mol enzyme tetramer) when the enzyme is maximally inactivated; this value corresponds to the number of reversible binding sites for each of the natural ligands of isocitrate dehydrogenase. The protection against oNAD or oNADH inactivation by NADH, NADPH, and ADP (but not by isocitrate, NAD, or NADP) indicates that reaction occurs in the region of a nucleotide regulatory site. In contrast to the effects of oNAD and oNADH, oNADP and oNADPH cause total inactivation of the NAD-dependent isocitrate dehydrogenase, concomitant with incorporation, respectively, of about 3.5 mol [14C]oNADP or 1.3 mol [14C]oNADPH/mol average subunit. Reaction rates exhibit a linear dependence on [oNADP] or [oNADPH] and protection by natural ligands against inactivation is not striking. These results imply that oNADP and oNADPH are acting in this case as general chemical modifiers and indicate the importance of the free adenosine 2'-OH of oNAD and oNADH for specific labeling of the NAD-dependent isocitrate dehydrogenase. The new availability of 2',3'-dialdehyde nicotinamide ribose derivatives of NAD, NADH, NADP, and NADPH may allow selection of the appropriate reactive coenzyme analog for affinity labeling of a variety of dehydrogenases.

Adenosine Diphosphate↗
PubMed1988

Purification and kinetic and structural properties of spinach leaf NADP-dependent nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase.

NADP-dependent nonphosphorylating D-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.9) from spinach leaves has been purified to apparent electrophoretic homogeneity by ammonium sulfate fractionation, molecular sieving on Sephadex G-200, DEAE-cellulose, and 2',5'-ADP-Sepharose affinity chromatography. The purified enzyme exhibited a specific activity of 15 mumol (mg protein)-1 min-1 and was characterized as a homotetramer with a native molecular weight of 195,000. Preincubation of the purified enzyme with NADP+ resulted in an almost twofold increase in enzymatic activity. The rate of activation was slower than the rate of catalysis, indicating that the enzyme has hysteretic properties. This behavior results in a lag phase during activity measurement of the enzyme preincubated without NADP+. Substrate interaction and product inhibition studies suggest a rapid equilibrium random BiBi mechanism for the reaction. Thiol modifying reagents, iodoacetamide and diamide, completely inactivated the purified enzyme. Inactivation by iodoacetamide exhibited pseudo-first-order kinetics with a rate constant of 0.17 min-1. D-Glyceraldehyde 3-phosphate effectively protected the enzyme against inactivation by thiol reagents, suggesting that modification occurred at or near the substrate-binding site. Complete inactivation of the dehydrogenase was correlated with incorporation of 8 mol [1-14C]iodoacetamide/mol enzyme. Total protection afforded by D-glyceraldehyde 3-phosphate against enzyme inactivation by iodoacetamide was correlated with a protection of 4 mol reactive residues/mol enzyme. On the basis of these results it is suggested that one sulfhydryl group per enzyme subunit is essential for catalysis in spinach leaf nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase. A kinetic and molecular mechanism for the reaction is proposed.

Ammonium Sulfate↗
PubMed1990

Modulation of spinach chloroplast NADP-glyceraldehyde-3-phosphate dehydrogenase by chaotropic anions.

Neutral salts enhanced the specific activity of chloroplast NADP-glyceraldehyde-3-phosphate dehydrogenase (D-glyceraldehyde-3-phosphate:NADP+ oxidoreductase (phosphorylating), EC 1.2.1.13) from spinach leaves. The ordering of the respective anions, according to the concentration for maximal stimulation, yielded the lyotropic (Hofmeister) series [SCN- (0.05 M), ClO-4 (0.08 M), Cl3CCO-2 (0.24 M), I- (0.35 M), Br- (0.6 M), Cl- (1.0 M)]; the more chaotropic the anion the less its concentration for maximal activation. Neither the NAD-linked activity of the chloroplast enzyme nor glyceraldehyde-3-phosphate dehydrogenases originating from cyanobacteria and rabbit muscle were stimulated by neutral salts. Chaotropic anions also enhanced the catalytic capacity of the chloroplast enzyme at concentrations lower than those required for the activation process. In the presence of 0.12 M NaBr the rate of catalysis was maximum whereas the highest conversion from the inactive to an active form was observed at 0.6 M NaBr. On the other hand, nonstimulatory concentrations of chaotropic anions lowered the concentration of ATP, Pi, and NADPH required for maximum stimulation of the specific activity (concerted hysteresis). On the basis that the enhancement of NADP-glyceraldehyde-3-phosphate dehydrogenase (and other chloroplast enzymes) by chaotropic anions paralleled the effect of organic solvents and reduced thioredoxin, it appeared that the modification of hydrophobic (intramolecular) interactions participates in the mechanism of light-mediated regulation.

Aldehyde Oxidoreductases↗
PubMed1991

Purification and properties of NADP-linked glucose-6-phosphate dehydrogenase from Acetobacter hansenii (Acetobacter xylinum).

The NADP-linked glucose-6-phosphate dehydrogenase from Acetobacter hansenii (formerly known as Acetobacter xylinum) has been purified to apparent homogeneity. The sequence of the 10 N-terminal amino acids was determined. The subunit molecular weight of the enzyme is 53,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; gel filtration studies under nondenaturing conditions revealed that the molecular weight of the enzyme is 200,000 to 220,000 at pH 6.5 and 9.5, suggesting that the native enzyme is a tetramer. Specificity studies at both pH 6.5 and 9.5 demonstrated that the enzyme is a typical NADP-preferring glucose-6-phosphate dehydrogenase. The enzyme's catalytic activity increases with increasing pH, kcat being approximately 4 times greater at pH 9.5 than at pH 6.7 and the Km for NADP+ being 3 times lower at the higher pH; but the Km for glucose 6-phosphate is nearly 20 times higher at pH 9.5 than at pH 6.7, suggesting that the enzyme is catalytically more efficient at the lower pH. At pH 6.7, initial velocity measurements, product inhibition by NADPH, and inhibition by glucosamine 6-phosphate yielded results that were consistent with a steady-state random mechanism. At pH 9.5, steady-state kinetic analyses suggested that the mechanism is ordered, with coenzyme binding first, but nonlinear double-reciprocal plots were observed in the presence of NADPH when glucose 6-phosphate was varied and a complete kinetic analysis was not undertaken. Among several nucleotides and potential inhibitory ligands examined, only 2',5'-ADP inhibited the enzyme significantly.

Amino Acid Sequence↗
PubMed1991

NADP(+)-malic enzyme from sugarcane leaves: structural properties studied by thermal inactivation.

The irreversible thermal inactivation of the sugarcane leaf NADP(+)-malic enzyme was studied at 50 degrees C and pH 7.0 and 8.0. Depending on the preincubation conditions, thermal inactivation followed mono- or biphasic first-order kinetics. A two-step behavior in the irreversible denaturation process was found when protein concentration was sufficiently low. The protein concentration necessary to obtain monlphasic thermal inactivation kinetics was lower at pH 8.0 than at pH 7.0. The results suggest that biphasic inactivation kinetics are the consequence of the existence of two different oligomeric forms of the enzyme (dimer and tetramer), with the dimer being more stable in regards to thermal inactivation. The effects of the substrate and essential cofactors on the thermostability and equilibrium between the dimeric and tetrameric enzyme forms were also studied. Depending on the pH, NADP+, L-malate, and Mg2+ all had a protective effect on the stability of the dimeric and tetrameric species during thermal treatment. However, these ligands showed different effects on the aggregation state of the enzyme. NADP+ and L-malate induced dissociation, especially at pH 8.0, whereas Mg2+ induced aggregation of the protein. By studying the thermal inactivation kinetics at 50 degrees C and different pH values it was observed that the equilibrium between dimers and tetramers was dramatically affected in the range of pH 7.0-8.0. These results suggest that an amino acid residue(s) in the protein with an apparent pKa value of 7.7 needs to be deprotonated to stabilize aggregation of the enzyme to the tetrameric form.

Enzyme Activation↗
PubMed1992

Complex formation between ferredoxin and ferredoxin-NADP+ reductase from Anabaena PCC 7119: cross-linking studies.

Ferredoxin-NADP+ reductase and ferredoxin from the cyanobacterium Anabaena PCC 7119 have been covalently cross-linked by incubation with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide. The covalent adduct, which shows a molecular mass consistent with a 1:1 stoichiometry of the two proteins, maintains nearly 60% of the NADPH-cytochrome c reductase activity of the enzyme saturated with ferredoxin and this value is considerably higher than when equimolar amounts of both proteins are assayed. No ternary complexes with Anabaena flavodoxin or horse heart cytochrome c were formed, suggesting that the binding site on the enzyme is the same for ferredoxin and flavodoxin and that ferredoxin-NADP+ reductase and cytochrome c bind at a common site on ferredoxin. In the noncovalent complex, titrated at pH 7, the oxidation-reduction potential of ferredoxin becomes 15 mV more negative and that of ferredoxin-NADP+ reductase 27 mV more positive compared to the proteins alone. When covalently linked, the midpoint potential of the enzyme has a value similar to that in the noncovalent complex, while the ferredoxin potential is 20 mV more positive compared to ferredoxin alone. The changes in redox potentials have been used to estimate the dissociation constants for the interaction of the different redox forms of the proteins, based on the value of 1.21 microM calculated for the oxidized noncovalent complex.

Anabaena↗
PubMed1995

The effect of N-bromosuccinimide on ferredoxin:NADP+ oxidoreductase.

Treatment of spinach leaf ferredoxin:NADP+ oxidoreductase (FNR) with N-bromosuccinimide (NBS), under conditions where approximately one tryptophan residue per enzyme was modified, resulted in a loss of between 80 and 85% of the activity of the enzyme when electron transfer from NADPH to either ferredoxin or 2,6-dichlorophenol-indophenol was measured. Amino acid analysis revealed no detectable modification by NBS of any FNR amino acids other than tryptophan. Complex formation with ferredoxin, but not with NADP+, prevented both the inhibition of activity and the modification of tryptophan caused by the treatment with NBS. Modification of one FNR tryptophan residue had no significant effect on the Km values of the enzyme for either ferredoxin or NADPH or on the binding constants for the FNR complexes with either ferredoxin or NADP+. NBS treatment had only very small effects on the absorbance and circular dichroism spectra of FNR and did not significantly affect either the oxidation-reduction midpoint potential of the FAD prosthetic group of the enzyme or inhibit the reduction of the FAD group by NADPH. These results raise the possibility that a tryptophan residue may play a role in the electron transfer between the FAD of FNR and the enzyme substrate, ferredoxin.

Bromosuccinimide↗
PubMed1994

Nucleotide sequence of a rice root ferredoxin-NADP+ reductase cDNA and its induction by nitrate.

A ferredoxin-NADP+ reductase (FNR) cDNA was isolated from a lambda gt 11 cDNA library constructed from the roots of nitrate-induced rice (Oryza sativa L. cv. Kinmaze) seedlings. The nucleotide sequence of this clone contains a 1134 nucleotide open reading frame. The N-terminal 62 amino acid stretch was assigned to the transit sequence, followed by 316 residues for the mature protein. The rice root FNR shows only 49% sequence identity to that of the leaf enzyme, but the regions of the binding sites to ferredoxin, NADP-PPi and NADP+ are highly conserved between the two enzymes. The root FNR mRNA was induced transiently by the addition of nitrate, but not by ammonia. The results support the view that the root FNR is involved in the nitrate assimilation in nonchlorophyllous tissues.

Amino Acid Sequence↗