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Genetic organization and expression of citrate permease in lactic acid bacteria.

Citrate is present in many natural substrates, such as milk, vegetables and fruits, and its metabolism by lactic acid bacteria (LAB) plays an important role in food fermentation. The industrial importance of LAB stems mainly from their ability to convert carbohydrates into lactic acid and, in some species, like Lactococcus lactis and Leuconostoc mesenteroides, to produce C4 flavor compounds (diacetyl, acetoin) through citrate metabolism. Three types of genetic organization and gene locations, involving citrate metabolism, have been found in LAB. Citrate uptake is mediated by a citrate permease, which leads to a membrane potential upon electrogenic exchange of divalent citrate and monovalent lactate. The internal citrate is cleaved into acetate and oxaloacetate by a citrate lyase, and oxaloacetate is decarboxylated into pyruvate by an oxaloacetate decarboxylase, yielding a pH gradient through the consumption of scalar protons.

Bacterial Proteins↗

Nucleotide sequence and functional properties of a sodium-dependent citrate transport system from Klebsiella pneumoniae.

The gene of the sodium-dependent citrate transport system from Klebsiella pneumoniae (citS) is located on plasmid pES3 (Schwarz, E., and Oesterhelt, D. (1985) EMBO J. 4, 1599-1603) and encodes a 446-amino acid protein. Transport of citrate via this citrate transport protein (CitS) is dependent on the presence of sodium ions and is inhibited by magnesium ions. The delta pH (pH gradient across the membrane) is the major driving force for uptake. It is postulated that, in analogy with the proton-dependent citrate carrier (CitH) of K. pneumoniae (van der Rest, M. E., Abee, T., Molenaar, D., and Konings, W. N. (1990) Eur. J. Biochem. 195, 71-77), only one of the protonated species of citrate is recognized by CitS and that citrate is translocated across the membrane in symport with protons and sodium ions. The hydrophobicity profile of CitS suggests that the protein is very hydrophobic and contains 12 membrane-spanning segments. These segments are not centered around a hydrophilic core as has been suggested for other transport proteins, but the protein is asymmetrical with seven transmembrane segments in front of a large hydrophilic loop and five after this loop. The amino acid sequence is highly similar to a citrate transport system of Lactococcus lactis subsp. lactis var. diacetylactis (CitP) (David, S., van der Rest, M. E., Driessen, A. J. M., Simons, G., and de Vos, W. M. (1990) J. Bacteriol. 172, 5789-5794) and less similar to CitH of K. pneumoniae. We conclude that the citS gene of K. pneumoniae encodes a sodium-dependent citrate transport system that belongs to a novel subclass of transport proteins.

Amino Acid Sequence↗

Comparison of 24 hours urinary citrate levels in urolithiasis patients and healthy controls.

OBJECTIVE: To identify the difference in urinary citrate excretion between Stone Formers (SF) and Healthy Volunteers (HV) as a metabolic risk factor, that predisposes to urinary stone formation and to compare levels of urinary citrate in (HV) with reference values. METHODS: The 24 hours urinary citrate was evaluated in 40 patients treated for renal citrate and declared stone free, and 40 age matched healthy adults taken as controls. Both the groups had a similar living environment, extrinsic factors, diet and similar genetic descent. RESULTS: There was no significant difference in urinary citrate excretion level among stone formers (mean 262 SD 197) and normal volunteer subjects (mean 269 SD 140). Using the previously defined normal values (200) of urinary citrate in the local population, 55% of stone patients in our study group were hypocitric. While using the same value, 45% of our normal volunteers were also hypocitric. If 320 was taken as normal limit, 70% of the patient's population and 72% of controls were hypocitric. The prevalence of hypocitraturia was similar in the age matched adult groups. CONCLUSION: Certain intrinsic factors in our local subjects may account for the high prevalence of urolithiasis than in western population. Although the urinary citrate excretion of stone patients is similar to normal volunteers, uniformly low urinary citrate excretion may be a feature as a nation and not a predisposing factor for the lithogenesis. This supports the view that there may be more often prominent influences in stone formers possibly of genetic origin.

Adult↗

Citrate in synovial fluid and its relation to inflammation and crystal presence.

OBJECTIVE: To investigate the role of citrate in the pathophysiology of arthritides with calcium pyrophosphate dihydrate (CPPD) crystals and/or apatite-like material. METHODS: We measured citrate concentrations in the plasma and synovial fluid (SF) of 23 joints whose SF contained these crystals and 33 joints without crystals. The SF originated from 25 joints each of patients with rheumatoid arthritis (RA) and primary osteoarthritis (OA) and 10 patients with various other inflammatory joint diseases. RESULTS: There was significant correlation between citrate concentrations in the SF and plasma with values globally twice as high in the SF as in the plasma. Citrate concentrations in the SF of patients whose SF contained CPPD crystals and/or apatite-like material were not significantly lower than those without crystals. On the other hand, citrate concentrations were significantly lower in the SF of patients with RA and other inflammatory joint diseases versus those with OA. CONCLUSION: We have no evidence that lower amounts of citrate in SF favor the presence of CPPD crystals or apatite-like material. Our results, however, do suggest a complex regulation of the citrate concentration in SF where cellular metabolic processes and citrates arising from the plasma and neighboring tissues probably interact to produce the levels recorded.

Adult↗

Oxalate accumulation from citrate by Aspergillus niger. II. Involvement of the tricarboxylic acid cyclase.

Carbon-14 was incorporated into oxalate and CO2 from either citrate-1,5-14C, succinate-1,4-14C, or fumarate-1,4-14C by cultures of Aspergillus niger pregrown on a medium which contained glucose as the sole carbon source and which did not allow citrate accumulation. In cell-free extracts of mycelium forming oxalate and CO2 from added citrate the following enzymes of the tricarboxylic acid (TCA) cycle were identified: citrate synthase CE 4.1.3.7), aconitate hydratase (EC4.2.1.3), NAD and NADP-dependent isocitrate dehydrogenase (EC 1.1.1.41, 1.1.1.42), (alpha-oxoglutarate dehydrogenase (EC 1.2.4.2), succinate dehydrogenase (EC 1.3.99.1), fumarate hydratase (EC 4.2.1.2), and malate dehydrogenase (EC 1.1.1.37). The in vitro activity of aconitate hydratase and of NADP-dependent isocitrate dehydrogenase was shown to be almost identical to the rate of in vivo degradation of citrate or to exceed this rate. The degradation of citrate to oxalate was inhibited completely by 9 mM fluoroacetate. It is concluded that the TCA cycle is involved in the formation of oxalate from citrate.

Aconitate Hydratase↗

Citrate for long-term hemodialysis: prospective study of 1,009 consecutive high-flux treatments in 59 patients.

BACKGROUND: Regional citrate anticoagulation during hemodialysis is performed in selected patients at highly specialized units. We postulated that routine use of citrate at a long-term dialysis ward is safe and efficient. METHODS: During a 2-year period, we studied 1,009 consecutive citrate-anticoagulated high-flux hemodialysis treatments performed in 59 patients at our long-term dialysis ward. We used a simple citrate infusion protocol, calcium-free dialysate, and intravenous calcium substitution. Simple and clear algorithms allowed adjustments of the calcium substitution rate and dialysate settings by the attending nurse. Adverse events; indications for citrate anticoagulation; clotting; technical data; blood ionized calcium, sodium, and potassium levels; and acid-base homeostasis were analyzed prospectively. RESULTS: Of the treatments, 99.6% were accomplished successfully. Two adverse events were attributed to citrate use. Overall, ionized calcium levels were stable during the procedures and electrolyte and acid-base balances were well controlled. The use of central venous catheters for dialysis was associated with paradoxical behavior of ionized calcium levels (increasing blood ionized calcium levels despite decreased calcium infusion). Anticoagulation was excellent. CONCLUSION: Routine use of citrate anticoagulation in the setting of a long-term hemodialysis ward is safe and efficient. Measured ionized calcium levels should be interpreted with care if central venous catheters are used for vascular access because they could be biased by recirculation.

Acid-Base Equilibrium↗

Citrate shows specific, dose-dependent lympholytic activity in neoplastic cell lines.

We have demonstrated cell membrane destruction activity by carboxylic acid derivatives (CADs) mainly tri-sodium citrate, in neoplastic cell lines and, to a far lesser extent, in normal human peripheral blood mononuclear cells (hPBMC). Flow cytometric (FACS) analysis was applied to Annexin-V and Propidium Iodide (PI) stained cells to evaluate the degree of the apoptosis induced by citrate in the following cell lines: CCRF-CEM (shortened to CEM), H9, and Jurkat (T-Cells), Raji and WIL2-NS (B-Cells), HL-60 (myeloblasts), K562 (myelocytes) and U937 (monocytes). We also tested normal hPBMC. Before staining with Annexin/PI, manual cell counts were performed on 24- and 48-h-old cell cultures. Cell supernatants were assayed for lactate dehydrogenase (LDH). LDH values in samples correlated with enhanced apoptosis by FACS analysis. For comparison, ascorbate and 2 other CADs including, acetate and lactate were also evaluated for the induction of apoptosis. In addition, the ability of tri-sodium citrate to induce apoptosis in the presence and the absence of several antineoplastic drugs, such as dexamethasone, arsenic trioxide, hydrocortisone, 6-mercaptopurine, and methotrexate were tested on Jurkat cells. FACS, LDH, and cell count values all demonstrated an enhanced degree of apoptotic cell death in Jurkat cells by citrate. In most of our investigated cells, except for the H9 cell line, citrate has induced a greater degree of apoptosis than acetate which induced a greater degree than lactate (see Fig. 1.0). The nature of the cell death by ascorbate appeared to be due to necrosis rather than apoptosis. Pilot studies on normal hPBMC showed that citrate alone or in combination with antineoplastic drugs caused minimal cell death. Thus citrate might be of benefit in some chemotherapy treatments in order to reduce drug toxicity or possibly enhance drug activities in certain neoplasias.

Acetic Acid↗

ROLES OF CITRATE AND ACETOIN IN THE METABOLISM OF STREPTOCOCCUS DIACETILACTIS.

Harvey, R. J. (University of California, Davis), and E. B. Collins. Roles of citrate and acetoin in the metabolism of Streptococcus diacetilactis. J. Bacteriol. 86:1301-1307. 1963.-Streptococcus diacetilactis was unable to use citrate as a source of energy for growth, but the addition of citrate to a lactose-containing medium increased the specific growth rate 35%. Besides serving as the precursor of acetoin, some of the pyruvate formed from citrate was incorporated into cell material, primarily into lipids. A constant fraction of the weight of new cells was synthesized from the pyruvate formed from citrate. The rate of entry of citrate into cells was independent of the growth rate, and the usual result was that more pyruvate was formed from citrate than was required for cell synthesis. All excess pyruvate was converted to acetoin. Thus, acetoin formation acts as a detoxification mechanism, a means of removing intracellular pyruvate not required for synthesis of cell material.

Acetoin↗

Probing the link between citrate and malonyl-CoA in perfused rat hearts.

Little is known about the sources of cytosolic acetyl-CoA used for the synthesis of malonyl-CoA, a key regulator of fatty acid oxidation in the heart. We tested the hypothesis that citrate provides acetyl-CoA for malonyl-CoA synthesis after its mitochondrial efflux and cleavage by cytosolic ATP-citrate lyase. We expanded on a previous study where we characterized citrate release from perfused rat hearts (Vincent G, Comte B, Poirier M, and Des Rosiers C. Citrate release by perfused rat hearts: a window on mitochondrial cataplerosis. Am J Physiol Endocrinol Metab 278: E846-E856, 2000). In the present study, we show that citrate release rates, ranging from 6 to 22 nmol/min, can support a net increase in malonyl-CoA concentrations induced by changes in substrate supply, at most 0.7 nmol/min. In experiments with [U-(13)C](lactate + pyruvate) and [1-(13)C]oleate, we show that the acetyl moiety of malonyl-CoA is derived from both pyruvate and long-chain fatty acids. This (13)C-labeling of malonyl-CoA occurred without any changes in its concentration. Hydroxycitrate, an inhibitor of ATP-citrate lyase, prevents increases in malonyl-CoA concentrations and decreases its labeling from [U-(13)C](lactate + pyruvate). Our data support at least a partial role of citrate in the transfer from the mitochondria to cytosol of acetyl units for malonyl-CoA synthesis. In addition, they provide a dynamic picture of malonyl-CoA metabolism: even when the malonyl-CoA concentration remains constant, there appears to be a constant need to supply acetyl-CoA from various carbon sources, both carbohydrates and lipids, for malonyl-CoA synthesis.

ATP Citrate (pro-S)-Lyase↗

Differential modulation of citrate synthesis and release by fatty acids in perfused working rat hearts.

The objective of this study was to test the effect of increasing fatty acid concentrations on substrate fluxes through pathways leading to citrate synthesis and release in the heart. This was accomplished using semirecirculating work-performing rat hearts perfused with substrate mixtures mimicking the in situ milieu (5.5 mM glucose, 8 nM insulin, 1 mM lactate, 0.2 mM pyruvate, and 0.4 mM oleate-albumin) and 13C methods. Raising the fatty acid concentration from 0.4 to 1 mM with long-chain oleate or medium-chain octanoate resulted in a lowering ( approximately 20%) of cardiac output and efficiency with unaltered O2 consumption. At the metabolic level, beyond the expected effects of high fatty acid levels on the contribution of pyruvate decarboxylation (reduced >3-fold) and beta-oxidation (enhanced approximately 3-fold) to citrate synthesis, there was also a 2.4-fold lowering of anaplerotic pyruvate carboxylation. Despite the dual inhibitory effect of high fatty acids on pyruvate decarboxylation and carboxylation, tissue citrate levels were twofold higher, but citrate release rates remained unchanged at 11-14 nmol/min, representing <0.5% of citric acid cycle flux. A similar trend was observed for most metabolic parameters after oleate or octanoate addition. Together, these results emphasize a differential modulation of anaplerotic pyruvate carboxylation and citrate release in the heart by fatty acids. We interpret the lack of effects of high fatty acid concentrations on citrate release rates as suggesting that, under physiological conditions, this process is maximal, probably limited by the activity of its mitochondrial or plasma membrane transporter. Limited citrate release at high fatty acid concentrations may have important consequences for the heart's fuel metabolism and function.

Aconitate Hydratase↗

Regulation of malate dehydrogenase activity by glutamate, citrate, alpha-ketoglutarate, and multienzyme interaction.

Binding experiments indicate that mitochondrial aspartate aminotransferase can associate with the alpha-ketoglutarate dehydrogenase complex and that mitochondrial malate dehydrogenase can associate with this binary complex to form a ternary complex. Formation of this ternary complex enables low levels of the alpha-ketoglutarate dehydrogenase complex, in the presence of the aminotransferase, to reverse inhibition of malate oxidation by glutamate. Thus, glutamate can react with the aminotransferase in this complex without glutamate inhibiting production of oxalacetate by the malate dehydrogenase in the complex. The conversion of glutamate to alpha-ketoglutarate could also be facilitated because in the trienzyme complex, oxalacetate might be directly transferred from malate dehydrogenase to the aminotransferase. In addition, association of malate dehydrogenase with these other two enzymes enhances malate dehydrogenase activity due to a marked decrease in the Km of malate. The potential ability of the aminotransferase to transfer directly alpha-ketoglutarate to the alpha-ketoglutarate dehydrogenase complex in this multienzyme system plus the ability of succinyl-CoA, a product of this transfer, to inhibit citrate synthase could play a role in preventing alpha-ketoglutarate and citrate from accumulating in high levels. This would maintain the catalytic activity of the multienzyme system because alpha-ketoglutarate and citrate allosterically inhibit malate dehydrogenase and dissociate this enzyme from the multienzyme system. In addition, citrate also competitively inhibits fumarase. Consequently, when the levels of alpha-ketoglutarate and citrate are high and the multienzyme system is not required to convert glutamate to alpha-ketoglutarate, it is inactive. However, control by citrate would be expected to be absent in rapidly dividing tumors which characteristically have low mitochondrial levels of citrate.

Animals↗

A new classification system predicting keratomalacia after trauma in vitamin A deficiency: sodium citrate does not prevent disease progression.

PURPOSE: The purpose of this study was to develop a classification system to predict keratomalacia after trauma in vitamin A-deficient eyes and to determine whether citrate impedes polymorphonuclear leukocyte infiltration into the cornea, thus preventing keratomalacia. METHODS: Preliminary classification studies showed that a 7.0-mm corneal epithelial scrape, before clinical findings of corneal xerosis, did not induce keratomalacia. Primary studies were conducted concurrently on the same animals to develop the classification system and test the effect of citrate in vitamin A deficiency. A 7.0-mm corneal epithelial scrape was performed on vitamin A-deficient eyes in various stages of corneal xerosis and treated as follows. Experiment 1: group 1, 10% citrate drops; group 2, phosphate buffer solution (PBS) drops; experiment II: group 3, drops and subconjunctival injection of 10% citrate; group 4, drops and subconjunctival injection of PBS. RESULTS: Corneal abrasion in eyes with 2+ corneal xerosis yielded keratomalacia in 50% of cases; the remainder healed with xerotic epithelium. Eighty-three percent of eyes with > 2+ xerosis developed keratomalacia after corneal abrasion, whereas only 7.1% of eyes with < 2+ xerosis advanced to this stage. In experiment I, 27% of citrate-treated eyes and 38% of PBS-treated eyes developed keratomalacia (not significant). In experiment II, two of six citrate-treated eyes perforated and one eye developed keratomalacia. One of six control PBS eyes perforated and four developed keratomalacia. CONCLUSION: We correlated the degree of corneal xerosis with the occurrence of keratomalacia after corneal trauma. This led to the development of a classification scale that is of research and clinical significance. Additionally, citrate did not significantly reduce keratomalacia or perforation in the vitamin. A-deficient eye.

Animals↗

Reproducibility and temporal stability of ADP-induced platelet aggregation: comparison of the anticoagulants sodium citrate and D-phenylalanyl-L-prolyl-L-arginyl-chloromethyl ketone.

We compared the reproducibility and temporal stability of ADP-induced aggregation of platelet-rich plasma anticoagulated with citrate or with D-phenylalanyl-L-prolyl-L-arginyl-chloromethyl ketone (PPACK), a thrombin inhibitor. Citrate- or PPACK-platelet-rich plasma (PRP) was stored at room temperature in capped plastic tubes or in plastic syringes from which all air was expelled. At intervals over 1-5 hr after venipuncture, platelet aggregation was induced by 1-1.5 microM ADP. Initially, the aggregation of PPACK-PRP was nearly twice that of citrate-PRP. The response of PPACK-PRP stored in the syringe remained essentially constant over the interval of study, in contrast to the responses of the other samples which declined with time. The improved stability of the response obtained from samples anticoagulated with PPACK was due to the absence of citrate, since PRP containing both citrate and PPACK became less responsive over time in a manner similar to PRP which contained only citrate. Anticoagulation with PPACK rather than citrate results in a more reproducible and stable aggregation response and more closely reproduces the in vivo environment of the platelet.

Adenosine Diphosphate↗

Cloning and expression of Klebsiella pneumoniae genes coding for citrate transport and fermentation.

Three Escherichia coli clones (DH1/Cit1, DH1/Cit2 and DH1/Cit3) capable of utilizing citrate as a sole carbon source were isolated from a cosmid bank of Klebsiella pneumoniae wild-type DNA. Two of these clones (DH1/Cit1 and DH1/Cit2) only grew aerobically on citrate minimal medium, the third clone (DH1/Cit3) could also be cultured under fermentative conditions. The aerobic as well as the anaerobic generation times of the three clones were from 4.5 to 7 h. Whereas clone DH1/Cit3 showed a pronounced lag phase on citrate when the cells were pre-grown in medium without citrate, clone DH1/Cit1 immediately started growth, while with clone DH1/Cit2 a short lag phase could be observed upon transfer to citrate minimal medium. Restriction analyses of the three plasmids showed that no common fragments had been cloned. The length of the inserts were 13 and 6 kb for the aerobic Cit+ clones and 27 kb (10 kb) for the anaerobic one. Cultures of the anaerobic Cit+ clone were analyzed by immunoblotting techniques and shown to contain oxaloacetate decarboxylase, which confers citrate utilization under anaerobic conditions to K. pneumoniae. Enzyme assays demonstrated the active state of this biotin-containing membrane protein. The specific activity in vesicle preparations from the E. coli clone was 30% of the wild-type K. pneumoniae vesicles. Citrate acts as an inducer of enzyme protein synthesis in the E. coli clone as it does in K. pneumoniae.

Biological Transport↗

Alkali absorption and citrate excretion in calcium nephrolithiasis.

The role of net gastrointestinal (GI) alkali absorption in the development of hypocitraturia was investigated. The net GI absorption of alkali was estimated from the difference between simple urinary cations (Ca, Mg, Na, and K) and anions (Cl and P). In 131 normal subjects, the 24 h urinary citrate was positively correlated with the net GI absorption of alkali (r = 0.49, p < 0.001). In 11 patients with distal renal tubular acidosis (RTA), urinary citrate excretion was subnormal relative to net GI alkali absorption, with data from most patients residing outside the 95% confidence ellipse described for normal subjects. However, the normal relationship between urinary citrate and net absorbed alkali was maintained in 11 patients with chronic diarrheal syndrome (CDS) and in 124 stone-forming patients devoid of RTA or CDS, half of whom had "idiopathic" hypocitraturia. The 18 stone-forming patients without RTA or CDS received potassium citrate (30-60 mEq/day). Both urinary citrate and net GI alkali absorption increased, yielding a significantly positive correlation (r = 0.62, p < 0.0001), with the slope indistinguishable from that of normal subjects. Thus, urinary citrate was normally dependent on the net GI absorption of alkali. This dependence was less marked in RTA, confirming the renal origin of hypocitraturia. However, the normal dependence was maintained in CDS and in idiopathic hypocitraturia, suggesting that reduced citrate excretion was largely dietary in origin as a result of low net alkali absorption (from a probable relative deficiency of vegetables and fruits or a relative excess of animal proteins).

Acidosis, Renal Tubular↗

Improved assay for mixtures of citrate and citric acid in systemic alkalizer solutions.

A modification of the USP method for the assay of systemic alkalizer solutions containing mixtures of citrate and citric acid is presented; it involves two titrations and ion-exchange chromatography. A diluted sample is tritiated with 0.02 N NaOH to find the free citric acid content. The eluate from cation-exchange chromatography of an equal volume of diluted sample is titrated with 0.02 N NaOH to assay for total citric acid. Subtracting the results of the first titration from the second provides the citrate content. Synthetic mixtures of potassium citrate-citric acid, potassium citrate-sodium citrate-citric acid, and sodium citrate-citric acid were prepared and assayed. The method was applied to commercially available preparations. The proposed method eliminates some significant errors of the compendial method, and the accuracy and reproducibility are equal or better than those obtained with the compendial method. Theoretically, the result obtained by the compendial method does not necessarily give the citrate content.

Chromatography, Ion Exchange↗

Citrate alterations in primary and metastatic human prostatic adenocarcinomas: 1H magnetic resonance spectroscopy and biochemical study.

The objectives of this study were to quantitatively verify the low levels of citrate previously observed in primary human prostatic adenocarcinomas and to determine whether citrate was further reduced in metastatic prostatic cancer. This was accomplished by comparison of citrate concentrations of DU 145 xenografts (a poorly differentiated human prostatic adenocarcinoma cell line grown in nude mice) with concentrations in primary human adenocarcinomas. Following in vivo 1H NMR studies of DU 145 xenografts, citrate concentrations of DU 145 xenografts and surgically removed primary prostatic adenocarcinoma tissue were determined by quantitative high resolution 1H NMR and enzymatic assay. The most significant findings of this study were that citrate concentrations in primary human adenocarcinomas (3.74 +/- 0.19 mumol/g wet weight) were significantly lower than those observed for normal and benign hyperplastic (BPH) prostatic tissues. Furthermore there was a further ten-fold reduction of citrate associated with DU 145 xenografts (0.31 +/- 0.028 mumole/g wet weight) compared with primary prostatic cancer. DU 145 xenografts also exhibited higher levels of uridine diphosphosugars and choline containing metabolites relative to primary prostatic adenocarcinomas. These findings support the hypothesis that citrate is low in primary prostatic cancer and further reduced in metastatic disease.

Adenocarcinoma↗

Concepts of citrate production and secretion by prostate. 1. Metabolic relationships.

Accumulation and secretion of extraordinarily high levels of citrate are principal functions of the prostate gland of humans and other animals. To achieve this, prostate secretory cells must possess unique metabolic relationships which distinguish them from virtually all other cells. Furthermore, citrate metabolism is markedly altered in benign prostatic hyperplasia (BPH) and in prostatic carcinoma (CA). This review assimilates existing information and presents current concepts related to 1) the pathway of metabolism associated with net citrate production, 2) the involvement of transporting mechanisms associated with citrate secretion, 3) energy implications of citrate production, 4) altered metabolic relationships in BPH and CA, and 5) the importance of citrate relationships as biochemical markers for characterizing prostate secretory epithelial cells. It is hoped that this review will bring attention to the importance and urgency of elucidating and understanding the metabolic relationships associated with citrate production by normal and neoplastic prostate epithelial cells. Research in these areas has been severely neglected despite the fact that the combined incidence of BPH and CA constitutes the most prevalent neoplastic disease among men.

Aspartic Acid↗