Stereochemistry of ornithine decarboxylase reaction

To determine the steric course of the reaction of bacterial ornithine decarboxylase [EC 4.1.1.17], we have carried out the decarboxylation of L-ornithine in 2H2O and that of DL-[2-2H]ornithine in H2O, and obtained putrescine bearing a single deuterium atom in the C-1 position. The stereochemistry of [1-2H]putrescine was established by conversion to 1-(2-pyrrolidinyl)-2-propanone with acetoacetate and the pro-S hydrogen-specific diamine oxidase from pea seedlings. Analysis of deuterium content by gas chromatography-mass spectrometry showed that the deuterium label was fully retained during the conversion of [1-2H]putrescine produced by the decarboxylation of L-ornithine in 2H2O to 1-(2-pyrrolidinyl)-2-propanone, in contrast with the considerable loss of label from [1-2H]putrescine which was produced by the decarboxylation of DL-[2-2H]ornithine in H2O. The extent of loss of the deuterium label was in good agreement with the estimated value based on the isotope effect in the diamine oxidase reaction. These results indicate that the introduced deuterium (or hydrogen) is in the pro-R position at C-1 of putrescine, and consequently the ornithine decarboxylase reaction proceeds with retention of configuration.     

Hydron transfer catalyzed by triosephosphate isomerase. Products of isomerization of (R)-glyceraldehyde 3-phosphate in D2O

The product distributions for the reactions of (R)-glyceraldehyde 3-phosphate (GAP) in D(2)O at pD 7.5-7.9 catalyzed by triosephosphate isomerase (TIM) from chicken and rabbit muscle were determined by (1)H NMR spectroscopy. Three products were observed from the reactions catalyzed by TIM: dihydroxyacetone phosphate (DHAP) from isomerization with intramolecular transfer of hydrogen (49% of the enzymatic products), [1(R)-(2)H]-DHAP from isomerization with incorporation of deuterium from D(2)O into C-1 of DHAP (31% of the enzymatic products), and [2(R)-(2)H]-GAP from incorporation of deuterium from D(2)O into C-2 of GAP (21% of the enzymatic products). The similar yields of [1(R)-(2)H]-DHAP and [2(R)-(2)H]-GAP from partitioning of the enzyme-bound enediol(ate) intermediate between hydron transfer to C-1 and C-2 is consistent with earlier results, which showed that there are similar barriers for conversion of this intermediate to the alpha-hydroxy ketone and aldehyde products (Knowles, J. R., and Albery, W. J. (1977) Acc. Chem. Res. 10, 105-111). However, the observation that the TIM-catalyzed isomerization of GAP in D(2)O proceeds with 49% intramolecular transfer of the (1)H label from substrate to product DHAP stands in sharp contrast with the 相似文献   

Heterogeneity of the sn-glycerol 3-phosphate pool in isolated hepatocytes, demonstrated by the use of deuterated glycerols and ethanol.

Hepatocytes were isolated from female rats and incubated with [1,1,3,3-2H4]glycerol or [2-2H]glycerol. The deuterium excess in phosphatidylcholines, sn-glycerol 3-phosphate and other organic acids was determined by g.l.c./mass spectrometry. The unlabelled fraction of the major phosphatidylcholines decreased exponentially, and the turnover was not changed by the presence of ethanol. The relative contribution of the two deuterated glycerols was about the same in the major phosphatidylcholine as in sn-glycerol 3-phosphate, indicating that formation by acylation of dihydroxyacetone phosphate is insignificant. [1,1,3,3-2H4]Glycerol had lost deuterium to a larger extent when it was incorporated in the phosphatidylcholine than when it was incorporated in sn-glycerol-3-phosphate, indicating that the phosphatidylcholines are formed from a separate pool of sn-glycerol 3-phosphate. Deuterium at C-2 was transferred between sn-glycerol 3-phosphate molecules to about 25%. Ethanol decreased the extent of deuterium transfer, the extent of glycerol uptake and the loss of deuterium at C-1 and C-3 in sn-glycerol 3-phosphate. The results indicate that the oxidation to dihydroxyacetone phosphate was inhibited by the NADH formed during ethanol oxidation. [2-2H]Glycerol also labelled an alcohol dehydrogenase substrate, malate and lactate, indicating oxidation of sn-glycerol 3-phosphate in the cytosol. The two acids appeared to be formed in reductions with different pools of NADH.     

Biosynthetic studies on the tropane ring system of the tropane alkaloids from Datura stramonium

Isotopic labelling experiments have been carried out in Datura stramonium root cultures with the following isotopically labelled precursors; [2H3]- [2-13C, 2H3]-, [1-13C, 18O2]-acetates, 2H2O, [2H3-methyl]-methionine, [2-13C]-phenyllactate, [3-2H]-tropine and [2'-13C, 3-2H]-littorine. The study explored the incorporation of isotope into the tropane ring system of littorine 1 and hyoscyamine 2 and revealed that deuterium from acetate is incorporated only into C-6 and C-7, and not into C-2 and C-4 as previously reported. Oxygen-18 was not retained at a detectable level into the C(3)-O bond from [1-13C, 18O2]-acetate. The intramolecular nature of the rearrangement of littorine 1 to hyoscyamine 2 is revealed again by a labelling study using [2'-13C, 3-2H]-littorine, [2-13C]-phenyllactate and [3-2H]-tropine.     

Studies on the metabolism of unsaturated fatty acids. XII. Reaction catalyzed by 2,4-dienoyl-CoA reductase of Escherichia coli

Incorporation of deuterium atoms from deuterium-labeled NADPH and 2H2O during the reaction catalyzed by 2,4-dienoyl-CoA reductase of Escherichia coli (E. coli) was investigated. When trans-2,cis-4-decadienoyl-CoA was incubated with 4R- or 4S-[4-2H1]NADPH in the presence of purified 2,4-dienoyl-CoA reductase, no deuterium was detected in the reaction product by gas chromatography-mass spectrometry after derivatization to its pyrrolidine amide. On the other hand, when the dienoyl-CoA was incubated in the presence of NADPH and the reductase in 2H2O, two deuterium atoms were incorporated: One deuterium atom was located at the C-4 position of trans-2-decenoate, and the other at the C-5 position. The UV and shorter wavelengths of the visible spectrum of the reductase solution revealed that the reductase contained flavin as a prosthetic group. Therefore it is considered that a hydrogen atom of NADPH was first transferred to the flavin moiety of the reductase, and then the hydrogen atom was rapidly exchanged for one in the medium before its direct transfer to the substrate.     

The synthesis and enzymic hydrolysis of (E)-2-[2,3-2H2]propenyl glucosinolate: confirmation of the rearrangement of the thiohydroximate moiety

(E)-2-[2,3-2H2]propenyl glucosinolate was synthesised starting from (E)-[3,4-2H2]but-3-en-1-ol, which was produced by reduction of but-3-yn-1-ol with deuterium gas in the presence of Lindlar's catalyst. The synthesis of (E)-2-[2,3-2H2]propenyl glucosinolate was completed via the nitro intermediate to form the basic desulphoglucosinolate skeleton. The (E)-2-[2,3-2H2]propenyl glucosinolate was fully characterised and deuterium NMR spectroscopy used to examine the rearrangement of the thiohydroximate to the isothiocyanate and thiocyanate.     

Biosynthesis of acaterin: mechanism of the reaction catalyzed by dehydroacaterin reductase

Dehydroacaterin reductase is an enzyme which catalyzes the final step of acaterin biosynthesis, that is, the reduction of the C-4/C-5 double bond of dehydroacaterin. The mechanism of the reduction was investigated with a cell-free preparation obtained from the acaterin-producing microorganism, Pseudomonas sp. A 92. Incubation of dehydroacaterin in the presence of [4,4- 2H2]NADPH or D2O followed by 2H NMR analysis of the resulting acaterin revealed that the deuterium atom from NADPH was incorporated into the C-5 position of acaterin, while the deuterium atom from D2O was introduced into the C-4 position. It was further demonstrated that the pro-R hydrogen at C-4 of NADPH was stereospecifically utilized in this reduction.     

Hydron transfer catalyzed by triosephosphate isomerase. Products of isomerization of dihydroxyacetone phosphate in D2O

The product distributions for the reactions of dihydroxyacetone phosphate (DHAP) in D(2)O at pD 7.9 catalyzed by triosephosphate isomerase (TIM) from chicken and rabbit muscle were determined by (1)H NMR spectroscopy using glyceraldehyde 3-phosphate dehydrogenase to trap the first-formed products of the thermodynamically unfavorable isomerization reaction, (R)-glyceraldehyde 3-phosphate (GAP) and [2(R)-(2)H]-GAP (d-GAP). Three products were observed from the reactions catalyzed by TIM: GAP from isomerization with intramolecular transfer of hydrogen (18% of the enzymatic products), d-GAP from isomerization with incorporation of deuterium from D(2)O into C-2 of GAP (43% of the enzymatic products), and [1(R)-(2)H]-DHAP (d-DHAP) from incorporation of deuterium from D(2)O into C-1 of DHAP (40% of the enzymatic products). The ratios of the yields of the deuterium-labeled products d-DHAP and d-GAP from partitioning of the intermediate of the TIM-catalyzed reactions of GAP and DHAP in D(2)O are 1.48 and 0.93, respectively. This provides evidence that the reaction of these two substrates does not proceed through a single, common, reaction intermediate but, rather, through distinct intermediates that differ in the bonding and arrangement of catalytic residues at the enediolate O-1 and O-2 oxyanions formed on deprotonation of GAP and DHAP, respectively.     

Enzymatic in situ determination of stereospecificity of NAD-dependent dehydrogenases

Amino acid racemases inherently catalyze the exchange of alpha-hydrogen of amino acids with deuterium during racemization in 2H2O. When the reactions catalyzed by alanine racemase (EC 5.1.1.1) and L-alanine dehydrogenase (EC 1.4.1.1), which is pro-R specific for the C-4 hydrogen transfer of NADH, are coupled in 2H2O, [4R-2H]NADH is exclusively produced. Similarly, [4S-2H]NADH is made in 2H2O with amino-acid racemase with low substrate specificity (EC 5.1.1.10) and L-leucine dehydrogenase (EC 1.4.1.9), which is pro-S specific. We have established a simple procedure for the in situ analysis of stereospecificity of C-4 hydrogen transfer of NADH by an NAD-dependent dehydrogenase by combination with either of the above two couples of enzymes in the same reaction mixture. When the C-4 hydrogen of NAD+ is fully retained after sufficient incubation, the stereospecificity of hydrogen transfer by a dehydrogenase is the same as that of alanine dehydrogenase or leucine dehydrogenase. However, when the C-4 hydrogen of NAD+ is exchanged with deuterium, the enzyme to be examined shows the different stereospecificity from alanine dehydrogenase or leucine dehydrogenase. Thus, we can readily determine the stereospecificity by 1H NMR measurement without isolation of the coenzymes and products.     

Synthesis of deuterium-labeled tetrahydrocortisol and tetrahydrocortisone for study of cortisol metabolism in humans

A method is described for the preparation of multi-labeled tetrahydrocortisol (3alpha,11beta,17alpha,21-tetrahydroxy-5beta-[1, 2,3,4,5-2H5]pregnan-20-one, THF-d5), allo-tetrahydrocortisol (3alpha,11beta,17alpha,21-tetrahydroxy-5alpha-[1 ,2,3,4,5-2H5]pregnan-20-one, allo-THF-d5), and tetrahydrocortisone (3alpha,17alpha,21-trihydroxy-5beta-[1,2,3,4,5-2H5]pre gnane-11,20-dione, THE-d5) containing five non-exchangeable deuterium atoms in the steroid ring A. Reductive deuteration at C-1, C-2, C-3, C-4, and C-5 of prednisolone or prednisone was performed in CH3COOD with rhodium (5%) on alumina under the deuterium atmosphere. The isotopic purities of the labeled compounds as [2H5]-form were estimated to be 86.17 atom%D for THF-d5, 74.46 atom%D for allo-THF-d5 and 81.90 atom%D for THE-d5, based on the ion intensities in the region of the molecular ion of methoxime-trimethylsilyl (MO-TMS) derivatives measured by GC-MS.     

Evidence for an arene oxide-NIH shift pathway in the transformation of naphthalene to 1-naphthol by Bacillus cereus

Bacillus cereus ATCC 14579 transformed naphthalene predominately to 1-naphthol. Experiments with [¹⁴C]naphthalene showed that over a 24 h period, B. cereus oxidized 5.2% of the added naphthalene. 1-Naphthol accounted for approximately 80% of the total metabolites. B. cereus incubated with naphthalene under the presence of ¹⁸O₂ led to the isolation of 1-naphthol that contained 94% ¹⁸O. The metabolism of [1-²H]-and [2-²H]-naphthalene by B. cereus yielded 1-naphthol which retained 95% and 94% deuterium, respectively, as determined by mass spectral analysis. NMR spectroscopic analysis of the deuterated 1-naphthol formed from [1-²H]-naphthalene indicated an NIH shift mechanism in which 19% of the deuterium migrated from the C-1 to the C-2 position. The ¹⁸O₂ and NIH shift experiments implicate naphthalene-1,2-oxide as an intermediate in the formation of 1-naphthol from naphthalene by B. cereus.Abbreviations HPLC High performance liquid chromatography - NMR nuclear magnetic resonance     

Studies on the mechanism of 3-ketosphinganine synthetase.

The biosynthesis of sphinganine and 4-D-hydroxysphinganine was studied in rat liver microsomes and whole cells of yeast (Hansenula ciferri). It was shown in both cases that the condensation of [2,3,3-2H3]serine and palmitic acid yielded long chain bases containing only two deuterium atoms, both of which were located on the terminal (C-1) carbon atom by combined gas-liquid chromatography/mass spectrometry. When the reaction with the liver microsomal system was carried out in 2H2O with the protium species of serine, the sphinganine contained a deuterium atom on C-2. These results suggest that the synthesis of 3-ketosphinganine involves the replacement of the alpha-hydrogen atom and the carboxyl group of serine by a proton from the medium and a palmitoyl group, rather than a previously proposed mechanism in which the alpha-hydrogen of serine is retained. Some stereochemical requirements of 3-ketosphinganine synthetase are discussed.     

Dinuclear macrocyclic polyamine zinc(II) complexes: syntheses, characterization and their interaction with plasmid DNA

The syntheses, characteristics of dinuclear macrocyclic polyamine zinc complexes and their interaction with plasmid DNA are reported. The two cyclen (1,4,7,10-tetraazacyclododecane) moieties are bridged by rigid and flexible linkages. The crystal structures of Zn2C27H43N8O15Cl4 [5c.(ClO4)3.2H2O] and Zn2C30H43N10O13Cl3 [5e.(ClO4)3.H2O] have been determined. The complexes crystallize in the monoclinic space group C2/c and P2(1)/c with the following unit cell parameters: 5c.(ClO4)3.2H2O: a=32.568(4)A, b=14.8593(17)A, c=19.443(2)A, alpha=90.00 degrees , beta=119.435(4) degrees , gamma=90.00 degrees , Dc=1.551 mg/m3, FW=956.71, F(000)=3932; 5e.(ClO4)3.H2O: a=15.807(2)A, b=16.756(2)A, c=16.161(2)A, alpha=90.00 degrees , beta=97.062(4) degrees , gamma=90.00 degrees , Dc=1.546 mg/m3, FW=988.83, F(000)=2032. The distance between the two Zn(II) ions is about 4.0 A. The structures show that two zinc ions can synergistically interact with the substrate DNA. With this novel structural characteristics, the dinuclear macrocyclic polyamine Zn(II) complexes via the synergetic effect between the two zinc ions can catalyze the cleavage of plasmid DNA (pUC18) with unprecedented speed at physiological conditions.     

Syntheses,characterization and X-ray structures of the fac-[RuCl3(NO)(dppe)] and the trans-[RuCl(NO)(dppe)2]2+ species

Trans-[RuCl(NO)(dppe)2]2+ species were prepared. The complexes have been characterized by microanalysis, IR and 31P[1H] NMR spectroscopy and cyclic voltammetry. The trans-[RuCl(NO)(dppe)2](ClO4)2 complex shows a reversible one-electron-reduction process at E(1/2) = 0.200 V and another one-electron-reduction irreversible process at -0.620 V, both centered at the NO+ group. The dissociation of the NO group from the trans-[RuCl(NO)(dppe)2]2+ after two one-electron reductions results in the formation of the trans- and cis-[RuCl2(dppe)2] isomers. The product of an electrolyzed solution of the same complex at -0.300 V shows an EPR signal consistent with the presence of the [RuCl(NO(0))(dppe)2]+ complex. Crystal data for trans-[RuCl(NO)(dppe)2]2+*[RuCl4(NO)(H2O)]*1/2[RuCl6]4-*2[H2O] (I) and trans-[RuCl(NO)(dppe)(2)]2+*2[RuCl4(NO)(CH3O)]-*3[CH3OH] (II) are as follow: (I) Space group P-1, a=10.4040(3) A, b=12.3470(4) A, c=23.5620(8) A, alpha=95.885(2) degrees, beta=99.608(2) degrees, gamma=104.378(2) degrees, R=0.0521; (II) space group P-1, a=10.9769(2) A, b=13.2753(3) A, c=24.0287(4) A, alpha=99.743(1) degrees, beta=95.847(1) degrees, gamma=97.549(1) degrees; R=0.0496. The fac-[RuCl3(NO)(dppe)] (III) complex has been also prepared; its crystal data are: space group P2(1)/n (No. 14), a=11.841(2) A, b=13.775(2) A, c=16.295(4) A, beta=92.81(2) degrees; R1=0.0395.     

Influence of CO2 and low concentrations of O2 on fermentative metabolism of the ruminal ciliate Polyplastron multivesiculatum.

The effects of ruminal concentrations of CO2 and oxygen on the end products of endogenous metabolism and fermentation of D-glucose by the ruminal entodiniomorphid ciliate Polyplastron multivesiculatum were investigated. The principal metabolic products were butyric, acetic, and lactic acids, H2, and CO2. 13C nuclear magnetic resonance spectroscopy identified glycerol as a previously unknown major product of D-[1-13C]glucose fermentation by this protozoan. Metabolite formation rates were clearly influenced by the headspace gas composition. In the presence of 1 to 3 microM O2, acetate, H2, and CO2 formation was partially depressed. A gas headspace with a high CO2 content (66 kPa) was found to suppress hydrogenosomal pathways and to favor butyrate accumulation. Cytochromes were not detected (less than 2 pmol/mg of protein) in P. multivesiculatum; protozoal suspensions, however, consumed O2 for up to 3 h at 1 kPa of O2. Under gas phases of greater than 2.6 kPa of O2, the organisms rapidly became vacuolate and the cilia became inactive. The results suggest that fermentative pathways in P. multivesiculatum are influenced by the O2 and CO2 concentrations that prevail in situ in the rumen.     

Stereochemistry of propionyl-coenzyme A and pyruvate carboxylations catalyzed by transcarboxylase.

The stereochemistry of the two half-reactions catalyzed by the biotin-containing enzyme, transcarboxy-lase from Propionobacteria shermanii, has been determined. The pro-R hydrogen at C-2 of propionyl-coenzyme A is replaced by CO2 in formation of the S isomer of methylmalonyl-CoA, defining the process as retention of configuration. This C-2 hydrogen is abstracted at a rate identical with product formation. For the other half-reaction, pyruvate to oxalacetate, the chiral methyl group methodology of Rose (I. A. Rose (1970), J. Biol. Chem. 245, 6052) was employed. First, it was determined with [3-2-He]pyruvate that a kinetic deuterium isotope effect of 2.1 occurs at Vmax in this carboxyl transfer, indicating that the necessary requirement for discrimination against heavy isotopes of hydrogen existed. Then, 3(S)-[3-2-H,3-H]pyruvate, generated from 3(S)-]E-2-H,3-H]phosphoglycerate, was carboxylated and the oxalacetate trapped as [3030H]malate using malate dehydrogenase. Exhaustive incubation of the tritiated malate (3-H/14-C = 1.95) with fumarase to labilize the pro-R hydrogen at C-3 resulted in release of 65% of the tritium into water. Reisolation of the malate after fumarase action yielded a 30H/14-C ration of 0.67, indicating 34% retention as expected. The theoretical enantiotopic distribution for the observed k1H/k2H of 2.1 is 68:32. Selective enrichment of tritium in the pro-R position at C-3 of malate indicates enzymatic carboxylation of pyruvate with retention of configuration in this half-reaction also.     

Influence of CO2 and low concentrations of O2 on fermentative metabolism of the ruminal ciliate Polyplastron multivesiculatum

The effects of ruminal concentrations of CO2 and oxygen on the end products of endogenous metabolism and fermentation of D-glucose by the ruminal entodiniomorphid ciliate Polyplastron multivesiculatum were investigated. The principal metabolic products were butyric, acetic, and lactic acids, H2, and CO2. 13C nuclear magnetic resonance spectroscopy identified glycerol as a previously unknown major product of D-[1-13C]glucose fermentation by this protozoan. Metabolite formation rates were clearly influenced by the headspace gas composition. In the presence of 1 to 3 microM O2, acetate, H2, and CO2 formation was partially depressed. A gas headspace with a high CO2 content (66 kPa) was found to suppress hydrogenosomal pathways and to favor butyrate accumulation. Cytochromes were not detected (less than 2 pmol/mg of protein) in P. multivesiculatum; protozoal suspensions, however, consumed O2 for up to 3 h at 1 kPa of O2. Under gas phases of greater than 2.6 kPa of O2, the organisms rapidly became vacuolate and the cilia became inactive. The results suggest that fermentative pathways in P. multivesiculatum are influenced by the O2 and CO2 concentrations that prevail in situ in the rumen.     

Chemical formation of 4-hydroxy-2,5-dimethyl-3[2H]-furanone from D-fructose 1,6-diphosphate

The selective chemical formation of 4-hydroxy-2,5-dimethyl-3[2H]-furanone (HDF) from D-fructose 1,6-diphosphate in the presence of reduced nicotinamide-adenine-dinucleotides (NAD(P)H) was investigated by means of HPLC-DAD and HPLC-UV-MS/MS. The temperature optimum for HDF formation was 30 degrees C, whereas the pH value (pH 3-10) and chemical nature of the buffer had no significant influence. A linear correlation of reaction time and D-fructose 1,6-diphosphate concentration with the obtained HDF yield was observed. Proteins appeared to have a stabilizing effect. The NAD(P)H were mandatory, even in the presence of protein, implying a non-enzymatic hydride-transfer to an unknown intermediate which finally leads to the selective formation of HDF. The hydride-transfer was confirmed by the application of selectively pro-4R or pro-4S deuterium labeled NADH resulting in each case in the formation of HDF exhibiting a deuterium labeling of approx 30% and employment of [4R,S-(2)H(2)]-NADH led to a deuterium labeling of approx 66%. The incubation of [1-(13)C]-D-fructose 1,6-diphosphate with [4R,S-(2)H(2)]-NADH revealed that the hydride is transferred to C-5 or C-6 of the D-fructose 1,6-diphosphate skeleton. Thus, a chemical HDF formation from D-fructose 1,6-diphosphate under physiological reaction conditions was shown and for the first time to our knowledge a non-enzymatic hydride-transfer from NADH to a carbohydrate structure was demonstrated.     

Isotopic exchange during derivatization of platelet activating factor for gas chromatography-mass spectrometry

One approach to the quantitative analysis of platelet activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycerol-3-phosphocholine; also referred to as AGEPC, alkyl glyceryl ether phosphocholine) is hydrolytic removal of the phosphocholine group and conversion to an electron-capturing derivative for gas chromatography-negative ion mass spectrometry. [2H3]Acetyl-AGEPC has been commonly employed as an internal standard. When 1-hexadecyl-2-[2H3]acetyl glycerol (obtained by enzymatic hydrolysis of [2H3]-C16:0 AGEPC) is treated with pentafluorobenzoyl chloride at 120 degrees C, the resulting 3-pentafluorobenzoate derivative shows extensive loss of the deuterium label. This exchange is evidently acid-catalyzed since derivatization of 1-hexadecyl-2-acetyl glycerol under the same conditions in the presence of a trace of 2HCl results in the incorporation of up to three deuterium atoms. Isotope exchange can be avoided if the reaction is carried out at low temperature in the presence of base. Direct derivatization of [2H3]-C16:0 AGEPC by treatment with pentafluorobenzoyl chloride or heptafluorobutyric anhydride also results in loss of the deuterium label. The use of [13C2]-C16:0 AGEPC as an internal standard is recommended for rigorous quantitative analysis.     

N-Salicylidenehydrazides as versatile tridentate ligands for dioxovanadium(V) complexes

The Schiff base ligand derived from salicylaldehyde and benzoic acid hydrazide (H2salhyph) reacts with potassium metavanadate in methanol solution to yield the potassium salt of the corresponding cis-dioxovanadium(V) complex K[VO2(salhyph)] (1). 1 crystallizes with one molecule of methanol in the monoclinic space group P2(1)/c with a = 1332.3(7), b = 669.9(2), c = 1809.0(8) pm, beta = 100.96(4) degrees, and Z = 4. The reactions of 1 with several proton acidic compounds including water, methanol, ethane-1,2-diol (H2ed), and proton acids lead to neutral monooxovanadium(V) and cis-dioxovanadium(V) complexes ([VO2(Hsalhyph)] (2); [V2O3(salhyph)2] (3); [VO(OMe)(salhyph)(HOMe)] (4); [VO(Hed)(salhyph)] (5)). The crystal structure of 2 (triclinic space group P1 with a = 677.79(5), b = 842.89(7), c = 1214.66(9) pm, alpha = 79.931(1), beta = 75.466(1), gamma = 73.391(1) degrees, and Z = 2) reveals that the protonation of the cis-dioxovanadium(V) complex 1 occurs at the hydrazide nitrogen atom of the ligand system. This was confirmed by the spectroscopic properties of the deuterium derivative.