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PubMed2004

Alteration of product specificity of Aeropyrum pernix farnesylgeranyl diphosphate synthase (Fgs) by directed evolution.

Directed evolution of the C25 farnesylgeranyl diphosphate synthase of Aeropyrum pernix (Fgs) was carried out by error-prone PCR with an in vivo color complementation screen utilizing carotenoid biosynthetic pathway enzymes. Screening yielded 12 evolved clones with C20 geranylgeranyl diphosphate synthase activity which were isolated and characterized in order to understand better the chain elongation mechanism of this enzyme. Analysis of these mutants revealed three different mechanisms of product chain length specificity. Two mutants (A64T and A64V) have a single mutation at the 8th amino acid upstream of a conserved first aspartate-rich motif (FARM), which is involved in the mechanism for chain elongation reaction of all prenyl diphosphate synthases. One mutant (A135T) carries a single mutation at the 7th amino acid upstream of another conserved region (141GQ142), which was recently found to be another important region controlling chain elongation of a type III C20 geranylgeranyl diphosphate synthase and Escherichia coli C15 farnesyl diphosphate synthase. Finally, one mutant carrying four mutations (V84I, H88R, I177 M and M191V) is of interest. Molecular modeling, site-directed mutagenesis and in vitro assays of this mutant suggest that product chain-length distribution can be also controlled by a structural change provoked by a cooperative interaction of amino acids.

Aeropyrum↗
PubMed2004

Crystallization and preliminary X-ray diffraction study of the farnesyl diphosphate synthase from Trypanosoma brucei.

Farnesyl diphosphate synthase (FPPS) catalyses the formation of farnesyl diphosphate from dimethylallyl diphosphate and isopentenyl diphosphate and is an RNAi-validated drug target in Trypanosoma brucei, the causative agent of African sleeping sickness. A T. brucei FPPS (390 amino acids) has been expressed in Escherichia coli and the recombinant protein has been crystallized in the absence and presence of the bisphosphonate inhibitor minodronate. Diffraction data were collected at 100 K using synchrotron radiation from both crystal types. Crystals obtained in the absence of minodronate belong to space group I222, with unit-cell parameters a = 61.43, b = 118.12, c = 120.04 A, while crystals grown in the presence of minodronate belong to space group C2, with unit-cell parameters a = 131.98, b = 118.10, c = 63.25 A, beta = 112.48 degrees. An initial model of the drug-free protein has been built using a homology model with the molecular-replacement method and refined to 3.3 A resolution. It shows mostly helical structure and resembles the structure of avian farnesyl diphosphate synthase, but with the addition of two loop regions.

Alkyl and Aryl Transferases↗
PubMed1997

Examination of the thiamin diphosphate binding site in yeast transketolase by site-directed mutagenesis.

The role of two conserved amino acid residues in the thiamin diphosphate binding site of yeast transketolase has been analyzed by site-directed mutagenesis. Replacement of E162, which is part of a cluster of glutamic acid residues at the subunit interface, by alanine or glutamine results in mutant enzymes with most catalytic properties similar to wild-type enzyme. The two mutant enzymes show, however, significant increases in the K0.5 values for thiamin diphosphate in the absence of substrate and in the lag of the reaction progress curves. This suggests that the interaction of E162 with residue E418, and possibly E167, from the second subunit is important for formation and stabilization of the transketolase dimer. Replacement of the conserved residue D382, which is buried upon binding of thiamin diphosphate, by asparagine and alanine, results in mutant enzymes severely impaired in thiamin diphosphate binding and catalytic efficiency. The 25-80-fold increase in K0.5 for thiamin diphosphate suggests that D382 is involved in cofactor binding, probably by electrostatic compensation of the positive charge of the thiazolium ring and stabilization of a flexible loop at the active site. The decrease in catalytic activities in the D382 mutants indicates that this residue might also be important in subsequent steps in catalysis.

Amino Acid Sequence↗
PubMed2005

Characterization of solanesyl and decaprenyl diphosphate synthases in mice and humans.

The isoprenoid chain of ubiquinone (Q) is determined by trans-polyprenyl diphosphate synthase in micro-organisms and presumably in mammals. Because mice and humans produce Q9 and Q10, they are expected to possess solanesyl and decaprenyl diphosphate synthases as the determining enzyme for a type of ubiquinone. Here we show that murine and human solanesyl and decaprenyl diphosphate synthases are heterotetramers composed of newly characterized hDPS1 (mSPS1) and hDLP1 (mDLP1), which have been identified as orthologs of Schizosaccharomyces pombe Dps1 and Dlp1, respectively. Whereas hDPS1 or mSPS1 can complement the S. pombe dps1 disruptant, neither hDLP1 nor mDLP1 could complement the S. pombe dLp1 disruptant. Thus, only hDPS1 and mSPS1 are functional orthologs of SpDps1. Escherichia coli was engineered to express murine and human SpDps1 and/or SpDlp1 homologs and their ubiquinone types were determined. Whereas transformants expressing a single component produced only Q8 of E. coli origin, double transformants expressing mSPS1 and mDLP1 or hDPS1 and hDLP1 produced Q9 or Q10, respectively, and an in vitro activity of solanesyl or decaprenyl diphosphate synthase was verified. The complex size of the human and murine long-chain trans-prenyl diphosphate synthases, as estimated by gel-filtration chromatography, indicates that they consist of heterotetramers. Expression in E. coli of heterologous combinations, namely, mSPS1 and hDLP1 or hDPS1 and mDLP1, generated both Q9 and Q10, indicating both components are involved in determining the ubiquinone side chain. Thus, we identified the components of the enzymes that determine the side chain of ubiquinone in mammals and they resembles the S. pombe, but not plant or Saccharomyces cerevisiae, type of enzyme.

Alkyl and Aryl Transferases↗
PubMed1997

The Saccharomyces cerevisiae mevalonate diphosphate decarboxylase is essential for viability, and a single Leu-to-Pro mutation in a conserved sequence leads to thermosensitivity.

The mevalonate diphosphate decarboxylase is an enzyme which converts mevalonate diphosphate to isopentenyl diphosphate, the building block of isoprenoids. We used the Saccharomyces cerevisiae temperature-sensitive mutant defective for mevalonate diphosphate decarboxylase previously described (C. Chambon, V. Ladeveve, M. Servouse, L. Blanchard, C. Javelot, B. Vladescu, and F. Karst, Lipids 26:633-636, 1991) to characterize the mutated allele. We showed that a single change in a conserved amino acid accounts for the temperature-sensitive phenotype of the mutant. Complementation experiments were done both in the erg19-mutated background and in a strain in which the ERG19 gene, which was shown to be an essential gene for yeast, was disrupted. Epitope tagging of the wild-type mevalonate diphosphate decarboxylase allowed us to isolate the enzyme in an active form by a versatile one-step immunoprecipitation procedure. Furthermore, during the course of this study, we observed that a high level of expression of the wild-type ERG19 gene led to a lower sterol steady-state accumulation compared to that of a wild-type strain, suggesting that this enzyme may be a key enzyme in mevalonate pathway regulation.

Alleles↗
PubMed2005

Functional analysis of two solanesyl diphosphate synthases from Arabidopsis thaliana.

Solanesyl diphosphate (SPP) is regarded as the precursor of the side-chains of both plastoquinone and ubiquinone in Arabidopsis thaliana. We previously analyzed A. thaliana SPP synthase (At-SPS1) (Hirooka et al., Biochem. J., 370, 679-686 (2003)). In this study, we cloned a second SPP synthase (At-SPS2) gene from A. thaliana and characterized the recombinant protein. Kinetic analysis indicated that At-SPS2 prefers geranylgeranyl diphosphate to farnesyl diphosphate as the allylic substrate. Several of its features, including the substrate preference, were similar to those of At-SPS1. These data indicate that At-SPS1 and At-SPS2 share their basic catalytic machinery. Moreover, analysis of the subcellular localization by the transient expression of green fluorescent protein-fusion proteins showed that At-SPS2 is transported into chloroplasts, whereas At-SPS1 is likely to be localized in the endoplasmic reticulum in the A. thaliana cells. It is known that the ubiquinone side-chain originates from isopentenyl diphosphate derived from the cytosolic mevalonate pathway, while the plastoquinone side-chain is synthesized from isopentenyl diphosphate derived from the plastidial methylerythritol phosphate pathway. Based on this information, we propose that At-SPS1 contributes to the biosynthesis of the ubiquinone side-chain and that At-SPS2 supplies the precursor of the plastoquinone side-chain in A. thaliana.

Alkyl and Aryl Transferases↗
PubMed2006

A soluble form of phosphatase in Saccharomyces cerevisiae capable of converting farnesyl diphosphate into E,E-farnesol.

After anion-exchange chromatography, the soluble fraction of a cell-free extract of Saccharomyces cerevisiae showed two phosphatase activity peaks when p-nitrophenyl phosphate (pNPP) was used as the substrate. However, only the second pNPP active peak demonstrated the ability to convert farnesyl diphosphate (FPP) into E,E-farnesol. N-terminal sequence analysis of the purified pNPP/FPP phosphatase revealed that it was a truncated form of alkaline phosphatase Pho8 lacking 62 amino acids from the N-terminus and was designated Pho8Delta62. Although other isoprenyl diphosphates such as geranyl diphosphate (GPP) and geranylgeranyl diphosphate (GGPP) could also be hydrolyzed by Pho8Delta62 to the corresponding alcohols, selectivity was observed among these substrates. The optimum pH was 7.0 for all three isoprenyl diphosphate substrates. Although lower hydrolytic activity was observed for FPP and GGPP at pH 6.0 and 8.5, hydrolysis of GPP was observed only at pH 7.0. Mg2+ and Mn2+ inhibited hydrolysis of FPP and GGPP, and GGPP was more sensitive to Mg2+ inhibition than FPP. The rate of FPP hydrolysis increased in the presence of Triton X-100.

Alkaline Phosphatase↗
PubMed2002

Pre-loading of chlorophyll synthase with tetraprenyl diphosphate is an obligatory step in chlorophyll biosynthesis.

The reaction of recombinant chlorophyll synthase from Avena sativa, expressed in Escherichia coli, was investigated. To verify the identity of the recombinant and native enzymes, reaction rates were determined for both enzyme preparations with several chlorophyllide analogs. The rates of esterification of these modified substrates ranged from 0 to 100% of the rate with the natural substrate, and were nearly identical for both enzyme preparations. The Lineweaver-Burk plot for variation of both chlorophyllide a and phytyl diphosphate concentration showed parallel lines, indicative of a 'ping-pong' mechanism. Pre-incubation with phytyl diphosphate exhibited an initial rapid reaction phase, which did not occur after pre-incubation with chlorophyllide. We conclude that the tetraprenyl diphosphate must bind to the enzyme as the first substrate and esterification occurs when this pre-loaded enzyme meets the second substrate, chlorophyllide. Approximately 10-17% of the recombinant enzyme were pre-loaded with phytyl diphosphate under the experimental conditions. The rapid reaction phase is also observed for the chlorophyll synthase reaction in etiolated barley leaves in addition to the well-known slow phase. This indicates that pre-loading of the enzyme with tetraprenyl diphosphate is also the basis for the reaction in vivo.

Avena↗
PubMed1992

Effects of site-directed mutagenesis of the highly conserved aspartate residues in domain II of farnesyl diphosphate synthase activity.

Comparison of the farnesyl diphosphate (FPP) synthase amino acid sequences from four species with amino acid sequences from the related enzymes hexaprenyl diphosphate synthase and geranylgeranyl diphosphate synthase show the presence of two aspartate rich highly conserved domains. The aspartate motif ((I, L, or V)XDDXXD) of the second of those domains has homology with at least 9 prenyl transfer enzymes that utilize an allylic prenyl diphosphate as one substrate. In order to investigate the role of this second aspartate-rich domain in rat FPP synthase, we mutated the first or third aspartate to glutamate, expressed the wild-type and mutant enzymes in Escherichia coli, and purified them to apparent homogeneity using a single chromatographic step. Approximately 12 mg of homogeneous protein was isolated from 120 mg of crude bacterial extract. The kinetic parameters of the purified wild-type recombinant FPP synthase containing the DDYLD motif were as follows: Vmax = 0.84 mumol/min/mg; GPP Km = 1.0 microM; isopentenyl diphosphate (IPP) Km = 2.7 microM. Substitution of glutamate for the first aspartate (EDYLD) decreased the Vmax by over 90-fold. The Km for IPP increased, whereas the Km for GPP remained the same in this D243E mutant. Substitution of glutamate for the third aspartate (DDYLE) did not result in altered enzyme kinetics in the D247E mutant. These results suggest that the first aspartate in the second domain is involved in the catalysis by FPP synthase.

Alkyl and Aryl Transferases↗
PubMed1991

Variable product specificity of microsomal dehydrodolichyl diphosphate synthase from rat liver.

Several detergents activated microsomal dehydrodolichyl diphosphate synthase of rat liver, but the chain length of products shifted downward from C90 and C95 with increasing concentration of the detergents. Maximum activation was observed at the concentration of 2% Triton X-100, 30 mM octyl glucoside, 30 mM 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, and 10 mM deoxycholate with the product chain length being C80-C85, C65-C75, C70-C75, and C55-C65, respectively. The activity of Triton X-100 solubilized enzyme was decreased by asolectin, phosphatidylethanolamine, and phosphatidylcholine. The chain lengths of products formed in the presence of these phospholipids were C85 and C90. In the presence of both phosphatidylcholine and Mg2+ the solubilized enzyme was able to produce C90 and C95 dehydrodolichyl diphosphates like native microsomal enzyme. Microsomal enzyme preparations from rat liver, brain, and testis catalyzed the formation of dehydrodolichyl diphosphates with the same chain lengths as those of the natural dolichols occurring in individual tissues. The chain length distribution of dehydrodolichyl products by (rat liver) microsomes also depended on the concentration of substrates. Not only did increasing the concentration of isopentenyl diphosphate lead to longer chain product, but decreasing that of farnesyl diphosphate increased product chain length.

Alkyl and Aryl Transferases↗
PubMedDate not supplied

[Thiamine diphosphate pool and its biosynthesis in the liver in galactosamine hepatitis].

The hepatitis-like changes were induced in the liver of albino female rats weighing 120-150 g and fed on the appropriate vivarium diet by single parenteral administration of hydrochloride galactosamine in a dose of 0.9 or 1.8 mmol per 1 kg of body weight. The thiamine diphosphate level in the cytosol fraction of the liver decreased 24 h after the preparation administration, the same in blood but with the higher dose used. The activity of pyruvate dehydrogenase, a thiamine diphosphate dependent enzyme, decreased similarly. The cytosol transketolase activity lowered by 38-39%. The coenzyme biosynthesis disturbance due to a fall by 49-58% in the thiamine pyrophosphatase activity is considered to be responsible for hydrochloride galactosamine-induced decrease in the thiamine diphosphate pool. Specificity of the thiamine diphosphate pool disturbance and discoordination of thiamine diphosphate dependent enzymes in the liver are observed under administration of hydrochloride galactosamine.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMedDate not supplied

[Interaction of pyruvate dehydrogenase complex from the heart muscle with thiamine diphosphate and its derivatives].

Inhibitory effects of 23 thiamin derivatives on the bovine heart pyruvate dehydrogenase complex (PDC) were studied. Oxythiamin diphosphate and tetrahydroxythiamin diphosphate exhibited the most pronounced effect on the PDC activity, affecting the complex by a competitive type of inhibition for thiamin diphosphate (TDP). The apparent affinity of TDP and the anticoenzyme derivatives for apo PDC depended on presence of phosphate and divalent metal ions. Phosphate considerably increased the Km values for TDP (up to 0.17 microM) and the Ki values for oxythiamin diphosphate (0.40 microM) as well as for tetrahydroxythiamin diphosphate (0.23 microM). In presence of Mn2+, Km value for TDP was 3.5-fold lower as compared with Mg2+ containing medium.

Animals↗
PubMed1987

Inability of fructose 1,6-diphosphate to reduce myocardial infarct size.

Fructose 1,6-diphosphate has been reported to reduce ischemic damage following coronary artery occlusion. To further evaluate fructose 1,6-diphosphate, we studied its effect on myocardial infarct size in open-chest, anesthetized dogs. Twenty min following left anterior descending coronary artery ligation, the animals received a constant infusion of either normal saline or fructose 1,6-diphosphate. Six hours following coronary artery ligation, the animals were killed and the hearts were sectioned from base to apex. Area at risk, infarct size, and infarct size expressed as a percentage of the area at risk were determined. Fructose 1,6-diphosphate had no effect on the amount of necrosis following coronary artery ligation. The area of necrosis expressed as a percentage of the left ventricle was similar in control (26 +/- 3%) and treated groups (24 +/- 4%). The area of necrosis expressed as a percentage of the area at risk was also similar in control and treated groups. Thus, in this model of myocardial ischemia, fructose 1,6-diphosphate does not reduce myocardial infarct size.

Animals↗
PubMed1984

Allosteric activation of rat liver cytosolic 3-hydroxy-3-methylglutaryl coenzyme A reductase kinase by nucleoside diphosphates.

Extensively purified rat liver cytosolic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase kinase was used to examine the role of ADP in inactivation of HMG-CoA reductase (EC 1.1.1.34). Solubilized HMG-CoA reductase was a suitable substrate for HMG-CoA reductase kinase. At sufficiently high concentrations of solubilized HMG-CoA reductase, reductase kinase activity approached that measured using microsomal HMG-CoA reductase as substrate. Inactivation of solubilized HMG-CoA reductase by HMG-CoA reductase kinase required both MgATP and ADP. Other nucleoside diphosphates, including alpha, beta-methylene-ADP, could replace ADP. HMG-CoA reductase kinase catalyzed phosphorylation of bovine serum albumin fraction V by [gamma-32P]ATP. This process also required a nucleoside diphosphate (e.g. alpha, beta-methylene-ADP). Nucleoside diphosphates thus act on HMG-CoA reductase kinase, not on HMG-CoA reductase. For inactivation of HMG-CoA reductase, the ability of nucleoside triphosphates to replace ATP decreased in the order ATP greater than dATP greater than GTP greater than ITP, UTP. TTP and CTP did not replace ATP. Both for inactivation of HMG-CoA reductase and for phosphorylation of bovine serum albumin protein, the ability of nucleoside diphosphates to replace ADP decreased in the order ADP greater than CDP, dADP greater than UDP. GDP did not replace ADP. Nucleoside di- and triphosphates thus appear to bind to different sites on HMG-CoA reductase kinase. Nucleoside diphosphates act as allosteric activators of HMG-CoA reductase kinase. For inactivation of HMG-CoA reductase by HMG-CoA reductase kinase, Km for ATP was 140 microM and the activation constant, Ka, for ADP was 1.4 mM. The concentration of ADP required to modulate reductase kinase activity in vitro falls within the physiological range. Modulation of HMG-CoA reductase kinase activity, and hence of HMG-CoA reductase activity, by changes in intracellular ADP concentrations thus may represent a control mechanism of potential physiological significance.

AMP-Activated Protein Kinases↗
PubMed1994

Purification of geranylgeranyl diphosphate synthase from bovine brain.

Geranylgeranyl diphosphate (GGPP) synthase was purified to homogeneity from bovine brain in a one-step affinity column procedure. For the construction of the affinity column, a farnesyl diphosphate (FPP) analog, O-(6-amino-1-hexyl)-P-farnesylmethyl phosphonophosphate, was synthesized and linked to the spacer of the matrix of Affigel 10 via the amino group. The native enzyme appeared to be homooligomer (150-195 kDa) with a molecular mass of the monomer of 37.5 kDa. The pI for the enzyme was 6.2. The Km values for dimethylallyl diphosphate (DMAPP), geranyl diphosphate (GPP) and FPP were estimated to be 33 microM, 0.80 microM and 0.74 microM, respectively. The Km value for isopentenyl diphosphate (IPP) in the presence of both IPP and FPP mixture was 2 microM. The ratio of the reaction velocity for formation of GGPP from DMAPP, GPP or FPP was 0.004:0.145:1. The intermediate FPP was formed in the reaction with GPP as an allylic primer. FPP synthase catalyzing the formation of FPP from DMAPP and IPP was also purified to homogeneity from the same organ by a similar affinity chromatography procedure using a GPP analog, O-(6-amino-1-hexyl)-P-geranylmethyl phosphonophosphate as a ligand. The enzyme was a homodimer with a monomeric molecular mass of 40.0 kDa. These results indicate that GGPP, a lipid precursor for the biosynthesis of a majority of prenylated proteins, is synthesized from DMAPP and IPP by the action of FPP synthase catalyzing the reactions C5-->C15 followed by the action of GGPP synthase catalyzing the reaction C15-->C20.

Alkyl and Aryl Transferases↗
PubMedDate not supplied

Effect of intravenous fructose-1,6-diphosphate on myocardial contractility in patients with left ventricular dysfunction.

STUDY OBJECTIVE: To examine the effects of fructose-1,6-diphosphate on myocardial performance using nuclear scintigraphy. DESIGN: Prospective, randomized, single-blind, parallel study. SETTING: Urban teaching hospital clinical research center. PATIENTS: Individuals with New York Heart Association functional class II-III heart failure (mild to moderate). INTERVENTIONS: Subjects received either intravenous fructose-1,6-diphosphate 125 mg/kg or normal saline 1.3 ml/kg every 12 hours over 10 minutes for four consecutive doses. Left ventricular performance was assessed by radionuclide ventriculography at baseline and within 60 minutes after the fourth infusion. Vital signs were monitored throughout the study period. MEASUREMENTS AND MAIN RESULTS: Fructose-1,6-diphosphate resulted in a modest 7% increase in left ventricular ejection fraction (p < 0.05). Peak ejection rate and peak diastolic filling rate did not change significantly. There were no changes in blood pressure or heart rate with either fructose-1,6-diphosphate or placebo. CONCLUSIONS: Fructose-1,6-diphosphate produces a modest but significant increase in left ventricular ejection fraction in patients with mild to moderate heart failure.

Adult↗
PubMed2002

The mechanism of phosphorylation of natural nucleosides and anti-HIV analogues by nucleoside diphosphate kinase is independent of their sugar substituents.

The reaction mechanism of the phosphoryl transfer catalyzed by dinucleoside diphosphate kinase from Dictyostelium discoideum is investigated by semiempirical AM1 molecular orbital computation of an active site model system on the basis of various X-ray crystallographic structures. The computational results suggest that the phosphoryl transfer from adenosine triphosphate to the His122 residue is accompanied by the simultaneous shift of a proton from the histidine residue to one of the oxygen atoms of the gamma phosphate group. This involves a doubly protonated His122 residue whilst this residue is neutral in its ternary complex with ADP and the transition state analogue AlF(3). The proposed mechanism is thus analogous to that of phosphoryl transfer by cyclic adenosine monophosphate dependent protein kinase and uridine/cytidine monophosphate kinase as found in our earlier work and clarifies the role of the ribose 3'-OH group. Furthermore, the energetics of phosphoryl transfer onto other nucleoside analogues such as 3'-azido-3'-deoxythymidine-diphosphate and 2',3'-dideoxy-2',3'-didehydro-thymidine-diphosphate are investigated. The calculated reaction barriers for the phosphorylation of the diphosphates by the enzyme are all within a range of 13.1 kJ mol(-1), which suggests that variations in the activation energies alone cannot account for the experimentally observed differences in enzymatic activity. Consequences for the design of new anti-HIV nucleoside analogues are discussed. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2268/2002/f360_s.pdf or from the author.

Adenosine Diphosphate↗
PubMed1976

Studies on nucleotide diphosphate diacylglycerol specificity of acidic phospholipid biosynthesis in rat liver subcellular fractions.

(1)Cytidine diphosphate diacylglycerol, uridine diphosphate diacylglycerol, adenosine diphosphate diacylglycerol and guanosine diphosphate diacylglycerol were synthesized chemically and their purity assessed. The acticity of these compounds in acidic phospholipid synthesis was examined in rat liver mitochondria and microsomes. (2) Phosphatidylglycerol synthesis in rat liver mitochondria exhibited considerable activity with CDP diacylglycerol (v 7.0 nmol mg-1 h-1). UDPdiacylglycerol (v 5.4) and ADP diacylglyc erol (v 4.2). GDP diacylglycerol activity was detectable but very low. (3) Diphophatidylglycerol formation in mitochondria and phosphatidylinositolsythesis in microsomes exhibited considerable more specificity for CDP diacylglycerol. However, at high concentrations, measurable diphosphaticylglycerol and phophatidylinositol synthesis was observed with the other liponucleotides. (4) Although considerable phosphatidylglycerol formation was observed with UDPdiacaylglycerol and ADP diacylglycerol, it is unlikelky that these compounds are of physiologic importance, at least in rat liver, since CTP:phophatidic acid cytidyltransferase in microsomes and mitochondria was shown to be specific for cytidine triphosphate. The lack of specificity of phosphatiidylglycerol synthesis for CDP diacylglycerol is currently unexplained but may be of some importance in other tissues or in other organisms.

Animals↗