Influence of adrenalectomy and steroid replacement on heart citrate synthase levels

Aldosterone-dependent changes in citrate synthase (CS) activity have been used as an index of mineralocorticoid target sites. However, adrenalectomy (ADX) resulted in a fall in activity of CS and several other enzymes in rabbit heart, a tissue with glucocorticoid-but not mineralocorticoid-specific receptors. The enzymes included CS (2.03-1.36 U/mg protein, normal----ADX, P less than 0.001), isocitrate dehydrogenase-NADP+ (1.10-0.80 U/mg, P less than 0.002), isocitrate dehydrogenase-NAD+ (0.034-0.020 U/mg, P less than 0.01), and hydroxymethylglutaryl-CoA lyase (0.072 to 0.035 U/mg, P less than 0.001); in contrast, mitochondrial malate dehydrogenase levels were not significantly reduced by adrenal loss. There was also a decrease after surgery in sarcolemmal Na-K-(17.30-12.31 mumol Pi . mg protein-1 . h-1, P less than 0.002) and Mg-ATPase activities (14.16-12.11 mumol Pi . mg protein-1 . h-1, P less than 0.05). However, ADX did not result in a significant change in heart weight per kilogram body weight or recovery of mitochondrial protein per gram heart. CS was also assayed in hearts from ADX animals following acute (90 min) and chronic (3 day) steroid replacement. Although neither acute intravenous aldosterone (10 micrograms/kg) nor dexamethasone (100 micrograms/kg) increased activity, exposure to multiple subcutaneous injections of either steroid over a 3-day period significantly elevated CS above ADX values. The coordinate changes in the levels of several myocardial enzymes associated with energy metabolism is discussed in terms of an adaptation to chronic alterations in energy demands as opposed to specific mineralocorticoid or glucocorticoid receptor-mediated processes.

Lipoamiddehydrogenase, Citratsynthase und?-Hydroxyacyl-CoA-dehydrogenase des Skelettmuskels III. Aktivit�t und subzellul�re Verteilung in heller und dunkler Muskulatur von Rind, Schwein und Gefl�gel

The extractable total activities of lipoamide dehydrogenase (LIPDH), citrate synthase (CS), and beta-hydroxyacyl-CoA-dehydrogenase (HADH) were determined in different muscles (longissimus dorsi, semimembranosus, diaphragma) from cattle and pigs, and in the breast and leg muscles from chicken and ducks. The subcellular distribution of these enzymes was elucidated by determination of the enzyme activities in the pressjuice of the intact muscle tissue. In the muscles of the different species positive correlations between myoglobin content and the activities of the three enzymes were found, which were closer for pigs and chicken than for cattle and ducks. At least 90 percent of the total activity of LIPDH, CS and HADH was located in the mitochondria.

Hypoxic coordinate regulation of mitochondrial enzymes in mammalian cells

The effect of hypoxic exposure on various mitochondrial enzymes and on cell mitochondrial genomic content was studied in two types of mammalian cells. Hypoxia depressed the activity of six enzymes to the same degree. The kinetics of depression and of recovery during reexposure to normoxia were statistically similar for three marker enzymes. Despite the global and symmetrical decrease in enzyme activities, mitochondrial DNA remained constant. This suggests either symmetrical loss of mitochondrial enzymes from all mitochondria or complete loss of enzymes from a subpopulation of mitochondria with retention of an intact mitochondrial genome.

Regional enzyme development in rat brain. Enzymes of energy metabolism

The development of several key enzymes of pyruvate and 3-hydroxybutyrate metabolism and of the tricarboxylic acid cycle was studied in six regions (cerebellum, medulla oblongata and pons, hypothalamus, striatum, mid-brain and cortex) of the neonatal, suckling and adult rat brain (2 days before birth to 60 days after birth). The enzymes whose developmental patterns were studied were: pyruvate dehydrogenase (EC 1.2.4.1), 3-hydroxybutyrate dehydrogenase (EC 1.1.1.30), citrate synthase (EC 4.1.3.7), NAD-linked isocitrate dehydrogenase (EC 1.1.1.41) and fumarase (EC 4.2.1.2). Citrate synthase, isocitrate dehydrogenase and pyruvate dehydrogenase develop as a cluster in each region, although the pyruvate dehydrogenase appears to lag slightly behind the others. As with the glycolytic-enzyme cluster [Leong & Clark (1984) Biochem. J. 218, 131-138] the timing of the development of the activity of this group of enzymes varies from region to region; 50% of the adult activity developed first in the medulla oblongata, followed by the hypothalamus, striatum and mid-brain, and then in the cortex and cerebellum respectively. The 3-hydroxybutyrate dehydrogenase activity also develops earlier in the medulla oblongata than in the other regions. The results are discussed with respect to the neurophylogenetic development of the brain regions studied and the importance of the development of the enzymes of aerobic glycolysis in relationship to the development of neurological maturation.

Regulation of enzymes by fatty acyl coenzyme A. Interactions of short and long chain spin-labeled acyl-CoA with the acetyl-CoA site on pig heart citrate synthase

The binding of two similar spin-labeled fatty acyl-CoA analogues, one short chain, 6-doxyloctanoyl-CoA (S-(2-(5-carboxybutyl)-2-ethyl-4, 4-dimethyl-3-oxazolidinyl-N-oxyl)-CoA) and one long chain, 6-doxylstearoyl-CoA (S-(2-(5-carboxybutyl)-2-dodecyl-4, 4-dimethyl-3-oxazolidinyl-N-oxyl)-CoA) to pig heart citrate synthase (citrate oxaloacetate-lyase (pro-3S-CH2COO- leads to acetyl-CoA) EC 4.1.3.7) has been compared. The binding of the short chain analogue could be satisfactorily fit by a classical treatment (independent, noninteracting sites) with well defined stoichiometry: 2 mol of spin label bound per mol of dimeric enzyme. Binding of the long chain analogue was complex and in excess of 2 mol/dimer. Competitive binding experiments using either analogue in the presence of various nucleotides and substrates revealed differences in the binding of the long and short chain analogues. These additional studies, together with kinetic measurements, implied isosteric binding of acyl-CoA, ATP, NADPH, NADH, NADP+, acetyl-CoA, and partial isosteric binding of the long chain acyl-CoA. Binding of NADPH and NADP+ to the same form of the enzyme, perhaps through overlapping sites, was kinetically verified even though these nucleotides had differing effects on the binding of the spin-labeled analogues. Oxalacetate was shown to decrease the binding of the long chain analogue but to have no effect on the binding of the short chain. This result was supported by kinetic measurements. The competitive binding experiments with the long chain analogue suggested that its complex isotherm resulted from binding in two classes of sites, i.e. two cooperative nucleotide sites and other sites. An empirical mathematical model employing this rationale provided a satisfactory fit for the binding of fatty acyl-CoA to citrate synthase. A spin-labeled fatty acid which was not bound by the native enzyme was appreciably bound in the presence of additional palmitoyl-CoA. This binding might be identified with one of the two sets of binding sites proposed in the model. These and previous results on acyl-CoA binding were correlated with the properties of the CoA binding site defined crystallographically (Remington, S., Wiegand, G., and Huber, R. (1982) J. Mol. Biol. 158, 111-152).

Characterisation of the citrate synthase reaction with propionyl-CoA

Experiments with propionyl-CoA stereoselectively deuteriated in the propionyl moiety demonstrate that the formation of (2S,3S)-methylcitric acid (1) catalysed by citrate (si)-synthase occurs with inversion of configuration in the propionyl moiety; the absolute configurations of the methylcitric acids 1 and 2 indicate a si attack on oxaloacetate. Deuterium in the pro-S position is exchanged for protium 60 times faster than deuterium in the pro-R position. Experiments with (R,S)-(2-2H1)propionyl-CoA allowed the determination of isotope effects. For the enzymatic formation of 1, a primary deuterium isotope effect kH/kD = 1.8 and a secondary alpha-deuterium isotope effect kH/kD = 0.99 were calculated; both are effects on Vmax/KM.

A study on the physical interaction between the pyruvate dehydrogenase complex and citrate synthase

In this paper, physicochemical evidence is given for the association between the pyruvate dehydrogenase complex (EC 1.2.4.1) and citrate synthase (EC 4.1.3.7) with two gel chromatographic techniques with poly(ethylene glycol) co-precipitation and with ultracentrifugation. Experiments with active enzyme gel chromatography indicate that citrate synthase also associates with pyruvate dehydrogenase complex in its functioning state. Citrate synthase binds to the isolated transacetylase core of pyruvate dehydrogenase complex, but in the binding to the whole pyruvate dehydrogenase complex the two other components of the complex are also involved. One pyruvate dehydrogenase complex can bind 10-11 citrate synthase dimers, and the dissociation constant is about 5.7-6.0 microM as determined by two independent methods. The association between the pyruvate dehydrogenase complex and citrate synthase raises the possibility of the dynamic compartmentation of acetyl-CoA in the mitochondria which results in the direction of acetyl-CoA from pyruvate towards citrate.

Analysis of the coordinate expression of 3-hydroxy-3-methylglutaryl coenzyme A synthase and reductase activities in Chinese hamster ovary fibroblasts

Decreased activities of both 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) synthase and HMG CoA reductase are observed in the presence of sterol in the Chinese hamster ovary (CHO) fibroblast. In three different genotypes of CHO cell mutants resistant to 25-hydroxycholesterol both enzyme activities exhibit a decreased response to 25-hydroxycholesterol compared to wild-type cells. Permanently repressed levels of both HMG CoA synthase and HMG CoA reductase activities are observed in another CHO mutant, phenotypically a mevalonate auxotroph. Mevinolin, a competitive inhibitor of HMG CoA reductase, has no effect on HMG CoA synthase activity measured in vitro. Incubation of CHO cells with sublethal concentrations of mevinolin produces an inhibition of the conversion of [14C]acetate to cholesterol and results in elevated levels of both HMG CoA synthase and HMG CoA reductase activities. Studies of CHO cells in sterol-free medium supplemented with cycloheximide indicate that continuous protein synthesis is not required for the maximal expression of HMG CoA synthase activity and provide an explanation for the lack of temporal similarity between HMG CoA synthase and reductase activities after derepression. These results support the hypothesis of a common mode of regulation for HMG CoA synthase and HMG CoA reductase activities in CHO fibroblasts.

Human myocardial and skeletal muscle enzyme activities: creatine kinase and its isozyme MB as related to citrate synthase and muscle fibre types

Activities of myocardial and skeletal muscle total creatine kinase (CK) and its isozyme MB were related to the oxidative capacity [measured as the citrate synthase (CS) activity] and to the contractile characteristics (estimated as the percentage of type I muscle fibres). Skeletal muscle biopsies were obtained both from physically trained and untrained men and myocardial biopsies from patients subjected to open-heart surgery performed because of mitral or aortic valve disease. Enzyme activities were determined on freeze-dried muscle specimens. The CK-MB activity was about twice as high in trained skeletal muscle as in untrained ones reaching the myocardial level. The total CK activity was about three times higher in skeletal muscle than in myocardium; the myocardium, however, had CS activity 3-4 times larger than that of skeletal muscle. A close correlation was demonstrated between activities of CK-MB on one hand and CS (r = 0.76) or percentage type I fibres (r = 0.83) on the other hand suggesting a connection between CK-MB activity and the oxidative capacity of the cell. This was in contrast to total CK where different regressions were obtained when comparing the myocardium and the skeletal muscle of trained or untrained men. In conclusion, CK-MB activity in trained skeletal muscle in athletes were similar to that in myocardium. CK-MB was related to the oxidative capacity and formation of cellular energy in skeletal and heart muscle.

Purification and properties of citrate lyase from Escherichia coli

Citrate lyase (EC 4.1.3.6) has been purified from Escherichia coli and the homogeneity of the preparation established from the three-component subunits obtained on sodium dodecyl sulfate/polyacrylamide gel electrophoresis. The purified enzyme has a specific activity of 120 mumol min-1 mg-1 and requires optimally 10 mM Mg2+ and a pH of 8.0 for the cleavage reaction. The native enzyme is polydispersed in the ultracentrifuge and in polyacrylamide gel electrophoresis. The enzyme complex is composed of three different polypeptide chains of 85 000, 54 000, 32 000 daltons. An estimate of subunit stoichiometry indicates that 1 mol of the largest polypeptide chain is associated with 6 mol each of the smaller ones. The polypeptide subunits have been isolated in pure state and their biological functions characterize. The 54 000-dalton subunit functions as the acyltransferase alpha subunit catalyzing the formation of citryl coenzyme A from citrate in the presence of acetyl coenzyme A and ethylenediaminetetraacetic acid. The 32 000-dalton subunit functions as the acyllyase beta subunit catalyzing the cleavage of (3S)-citryl coenzyme A to oxal-acetate and acetyl coenzyme A. The 85 000-dalton subunit, which carries exclusively the prosthetic group components, functions as the acyl-carrier protein gamma subunit in the cleavage of citrate in the presence of mg2+ and the alpha and beta subunits. The presence of a large ACP subunit and the unusual stoichiometry of the different subunits distinguish the complex from other citrate lyases. A ligase which acetylates the deacetyl[citrate lyase] in the presence of acetate and ATP has ben shown to be present in the organism.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of endurance-training on the maximum activities of hexokinase, 6-phosphofructokinase, citrate synthase, and oxoglutarate dehydrogenase in red and white muscles of the rat

Adult female rats were subjected to an eleven-week endurance-training programme, and, for the first time, the maximum activities of enzymes that can indicate the quantitative capacities of both anaerobic glycolysis and the Krebs cycle in muscle (viz. 6-phosphofructokinase and oxoglutarate dehydrogenase respectively) were measured in heart plus white and fast-oxidative skeletal muscle. No changes were observed in heart muscle. In fast-oxidative skeletal muscle, activities of hexokinase, citrate synthase, and oxoglutarate dehydrogenase were increased by 51, 26, and 33% respectively but there was no effect on 6-phosphofructokinase. These results demonstrate that in red muscle there is no effect of this training programme on the anaerobic capacity but that of the aerobic system is increased by one third. In white skeletal muscle, only the activity of citrate synthase was increased, which indicates that this activity may not provide even qualitative information about changes in capacity of the Krebs cycle.

S-acylated residues of the acyl-carrier protein subunit of Klebsiella aerogenes citrate lyase

Oxidation of the isolated deacetyl acyl-carrier protein subunit of citrate lyase from Klebsiella aerogenes with Cu2+-o-phenanthroline complex leads exclusively to intrapeptide disulfide bridge formation indicating that the cysteamine and the cysteine residues are located in close proximity. The S-acetylation of the cysteine residue in deacetyl acyl-carrier protein subunit is catalysed by a citrate lyase ligase preparation in presence of acetate and ATP. Reaction-inactivation of citrate lyase results in deacetylation of the S-acetyl cysteamine residue of the prosthetic group but not of the S-acylated cysteine residue in the acyl-carrier protein.

Hysteretic behaviour of citrate synthase. Alternating sites during the catalytic cycle

Chemically and stereochemically pure (3S)-citryl-CoA was prepared enzymically and used as a substrate for citrate synthase to investigate the previously determined unexpectedly low rate of hydrolysis of the (3RS)-substrate. The unnatural R-diastereomer of this mixture is not inhibitory. At low enzyme concentrations the rate of citryl-CoA hydrolysis was linear until the reaction went near to completion; the hydrolysis approached Michaelis-Menten kinetics at high enzyme concentrations. In between these concentration extremes a biphasic rate dependence was detectable, where a fast initial phase lasting a few seconds was followed by a slow steady-state phase. Citrate synthase was characterized as a hysteretic enzyme existing in two interconvertible forms, which were designated according to their functions as hydrolase E and ligase E'. The hysteretic behaviour originates in the cleavage of citryl-CoA to acetyl-CoA and oxaloacetate. This reaction occurs on the ligase form E', which represents a trap for enzyme form E, the hydrolase. The conclusions given above are strengthened by the ordinary hydrolysis kinetics of (2S)-malyl-CoA, a substrate that is not subject to cleavage of the C-C bond on the synthase. The results satisfy the kinetic criterion for citryl-CoA being an intermediate of the physiological synthase reaction and, therefore, establish the oscillation of the synthase between hydrolase and ligase states during the catalytic cycle. A disorganization of these oscillations can be achieved by limited tryptic proteolysis of the synthase.

Stereospecificity in meta-fission catabolic pathways

The stereospecificities of 2-keto-4-pentenoate hydratase and 4-hydroxy-2-ketovalerate aldolase were studied in Escherichia coli, Pseudomonas putida, and Acinetobacter sp. Hydration was stereospecific in all three; however, only P. putida and Acinetobacter sp. showed stereospecificity in their aldolase reactions.

Citrate synthase from a Gram-positive bacterium. Purification and characterization of the Bacillus megaterium enzyme

Citrate synthase was purified to homogeneity from a Gram-positive bacterium (Bacillus megaterium) for the first time. The Mr of the native enzyme was determined to be 84 000 (S.E.M. +/- 5000). Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and gel filtration in guanidinium chloride revealed a single protein species of Mr 40 300 (S.E.M. +/- 4400), indicating a dimeric enzyme. This dimeric structure was confirmed by cross-linking the native enzyme with dimethyl suberimidate and with glutaraldehyde, followed by electrophoretic analysis. The enzyme follows Michaelis-Menten kinetics with respect to both substrates, acetyl-CoA and oxaloacetate, and is sensitive to non-specific inhibition by a range of adenine nucleotides. In both molecular and catalytic properties the citrate synthase closely resembles the enzyme from eukaryotic sources and contrasts markedly with the larger, hexameric, enzyme from Gram-negative bacteria.

Leucine catabolism during the differentiation of 3T3-L1 cells. Expression of a mitochondrial enzyme system

Leucine can be utilized efficiently as a precursor for lipid biosynthesis by adipose tissue, especially in the presence of glucose or glucose and insulin. During the differentiation of 3T3-L1 fibroblasts to adipocytes, the rate of lipid biosynthesis from L-[U-14C]leucine increases at least 30-fold and lipogenesis, with [U-14C] acetate as the precursor, increases by 10- to 15-fold. The specific activities of two mitochondrial dehydrogenases in the leucine oxidative pathway, the branched chain alpha-ketoacid dehydrogenase and isovaleryl-CoA dehydrogenase, as well as of leucine:alpha-ketoglutarate transaminase, increase at least 20-fold during the adipose conversion. Isovaleryl-CoA dehydrogenase was assayed in crude extracts using a specific fluorimetric method employing electron transfer flavoprotein as the electron acceptor for the flavoprotein dehydrogenase. The specific activity of 3-hydroxy-3-methylglutaryl-CoA lyase, the mitochondrial enzyme catalyzing the terminal reaction in the leucine degradation pathway, increases 4-fold during differentiation. The increases in the specific activities of the mitochondrial enzymes occur without a change in the specific activity of cytochrome oxidase, indicating that the increases do not simply reflect proliferation of mitochondria. The biosynthesis of at least 20 soluble mitochondrial polypeptides is enhanced during the adipose conversion of the fibroblasts as determined by polyacrylamide gel electrophoresis following incubation of the cells with [35S] methionine. The results provide a conservative estimate of the extent of changes in mitochondrial soluble proteins during the adipose conversion. They also establish that differentiated 3T3-L1 adipocytes metabolize leucine like mature adipose tissue and illustrate the roles of the branched chain alpha-ketoacid dehydrogenase and isovaleryl-CoA dehydrogenase in lipogenesis.

Oligomerization of malate synthase during glyoxysome biosynthesis

The octameric malate synthase, found in glyoxysomes of plants, is synthesized as monomeric precursor in the cytoplasm. The precursor form does not possess a different subunit molecular weight than the mature organellar enzyme, but differs from the organellar protein by not oligomerizing and aggregating. This was shown by synthesis in a cell-free reticulocyte lysate system programmed with cucumber poly A+-mRNA followed by immunoprecipitation of the radiolabeled translation products. The precursor form of malate synthase was also detected in vivo in the cytosol of pulse-labeled cucumber cotyledons after immunoprecipitation of the radiolabeled polypeptide. At low salt concentrations, mature malate synthase can be converted into aggregated forms. However, the precursor form obtained either by in vitro translation or by extraction from the cytosol after short pulses of radioactive methionine, could neither be oligomerized into the octameric form nor aggregated into the 100-S form. Processing of malate synthase, assumed to be a requisite for oligomerization, took place rapidly in the glyoxysomes, but proceeded only slowly in the cytosol. This was demonstrated both by the uptake of in vitro-translated malate synthase into glyoxysomes, and by analysis of newly synthesized malate synthase detectable in glyoxysomes in vivo. In both cases the octamer was by far the predominant form.

Malate synthase: aggregation, deaggregation, and binding of phospholipids

Octameric malate synthase is located in the glyoxysomes of cucumber cotyledons. The enzyme is predominantly confined to the organelle's membrane and can be solubilized with Mg2+. Separation of cell structures in a zonal rotor afforded, besides glyoxysomes, two other zones with malate synthase activity, viz., in the gradient supernatant and in the range of the endoplasmic reticulum (ER). Malate synthases of these three fractions were purified to apparent homogeneity and classified according to their molecular weight. Differences in subunit molecular weight, however, could not be detected when malate synthases from the three fractions were compared. Mature malate synthase, as well as malate synthase prepared from fractions sedimenting similarly to the ER, exhibited the following behavior with respect to aggregation and deaggregation: at low salt concentrations and in the absence of Mg2+, the enzyme shifted to aggregated forms (approx 100 S); with 2 mM Mg2+, malate synthase deaggregated and occurred predominantly as an octamer (19 S). By changing buffer conditions, mature forms of malate synthase could be interconverted repeatedly between octameric and aggregated forms, whereas a monomeric form (5 S), prepared from soluble fractions assigned to the cytosol, did not oligomerize. The amphipathic properties of malate synthase were demonstrated by the enzyme's capacity for binding phospholipids.

3-hydroxy-3-methylglutaryl-CoA lyase: catalysis of acetyl coenzyme A enolization

3-Hydroxy-3-methylglutaryl-CoA lyase, which performs the cleavage of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) to acetoacetate and acetyl-CoA by a Claisen-type reaction, also catalyzes enolization of acetyl-CoA. The rate of detritiation of methyl-labeled acetyl-CoA is proportional to enzyme concentration and is diminished by an antiserum that also inhibits the cleavage reaction. The tritium-exchange reaction requires both divalent cation and acetoacetate. An analogue of HMG-CoA, 3-hydroxyglutaryl-CoA, was prepared by reaction of acetonedicarboxylic anhydride with CoASH and reduction of the ketoacyl-CoA product with cyanohydridoborate. While 3-hydroxyglutaryl-CoA does not appear to be a substrate for HMG-CoA lyase, it competitively inhibits both the cleavage reaction (Ki = 50 microM) and the tritium exchange from acetyl-CoA (Ki = 95 microM). Agreement between the Ki values measured for cleavage and for tritium exchange supports the hypothesis that the slow tritium exchange is a lyase-dependent reaction. Initial attempts to demonstrate complete reversibility of the cleavage reaction have not been successful. However, the data suggest that the cleavage of HMG-CoA is at least partially reversible and indicate that enolization of acetyl-CoA may be dependent upon a conformational change of HMG-CoA lyase, induced by binding of acetoacetate, in a manner analogous to the keto acid dependent tritium exchange catalyzed by malate synthase and citrate synthase.

A survey of enzymes which generate or use acetoacetyl thioesters in rat liver

Reactions that generate and remove acetoacetyl-CoA and acetoacetate were measured in mitochondria and cytosol of rat liver. The activities surveyed include acetoacetyl-CoA hydrolase, acetoacetyl-glutathione hydrolase, acetoacetyl-CoA:glutathione acyl transferase, 3-ketothiolases I and II, 3-hydroxy-3-methylglutaryl-CoA lyase and synthase, and acetoacetyl-CoA synthetase. Phosphocellulose chromatography shows that cytosol contains at least four acetoacetyl-CoA hydrolase activities, two of which do not coincide with 3-ketothiolases or 3-hydroxy-3-methylglutaryl-CoA lyase, while mitochondria contain at least three acetoacetyl-CoA hydrolase activities that overlap partially or completely with 3-ketothiolases and 3-hydroxy-3-methyl-glutaryl-CoA lyase. Two of the mitochondrial acetoacetyl-CoA hydrolase activities are not found in cytosol. Cytosol contains at least two and mitochondrial extracts at least six acetoacetyl-glutathione hydrolase activities. Mitochondria and cytosol both contain two isozymes of 3-ketoacyl-CoA thiolase (thiolases Ia and Ib). Chain length specificities show that the mitochondrial and cytosolic forms of thiolase Ia differ from each other. We report a new isozyme of 3-ketoacyl-CoA thiolase (thiolase I) in rat liver cytosol.

Binding of citrate synthase to mitochondrial inner membranes

Citrate synthase and other mitochondrial matrix proteins bind to the inner surface of the mitochondrial inner membrane. No binding was observed to the outer membrane or to the outer surface of the inner membrane.