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At least 955 records · Page 53Linked to original sources
PubMed1992

Proline-directed phosphorylation of human Tau protein.

The primary sequence of the microtubule-associated protein tau contains multiple repeats of the sequence -X-Ser/Thr-Pro-X-, the consensus sequence for the proline-directed protein kinase (p34cdc2/p58cyclin A). When phosphorylated by proline-directed protein kinase in vitro, tau was found to incorporate up to 4.4 mol of phosphate/mol of protein. Isoelectric focusing of the tryptic phosphopeptides demonstrated the presence of five distinct peptides with pI values of approximately 6.9, 6.5, 5.6-5.9, 4.7, and 3.6. Mapping of the tryptic phosphopeptides by high performance liquid chromatography techniques demonstrated three distinct peaks. Data from gas phase sequencing, amino acid analysis, and phosphoamino acid analysis suggest that proline-directed protein kinase phosphorylates tau at four sites. Each site demonstrates the presence of a proline residue on the carboxyl-terminal side of the phosphorylated residue. Two phosphorylation sites are located adjacent to the three-repeat microtubule-binding domain that has been found to be required for the in vivo co-localization of tau protein to microtubules. Two other putative phosphorylation sites are located within the identified epitope of the monoclonal antibody Tau-1. Phosphorylation of these sites altered the immunoreactivity of tau to Tau-1 antibody. Since the neuronal microtubule-associated protein tau is multiply phosphorylated in Alzheimer's disease, and Tau-1 immunoreactivity is similarly reduced in neurofibrillary tangles and enhanced after dephosphorylation, phosphorylation at one or more of these sites may correlate with abnormally phosphorylated sites in tau protein in Alzheimer's disease.

Amino Acid Sequence↗
PubMed1995

The influence of proline analogs on bleomycin-induced lung injury in rats.

The influence of 3,4-dehydro-DL-proline and 3,4-dehydro-L-proline on lysyl oxidase, prolyl hydroxylase activities, collagen cross-linking and types of collagen in bleomycin-induced lung injury was investigated. Both proline analogs cause a great fall in prolyl hydroxylase activity without effect on lysyl oxidase, diminish the number of cross-links and normalize the type I/type III collagen ratio. It is suggested that proline analogs may be valuable agents in lung fibrosis treatment.

Aminoglycosides↗
PubMed1996

Functional characterization of NCAM fibronectin type III domains: demonstration of modulatory effects of the proline-rich sequence encoded by alternatively spliced exons a and AAG.

In order to characterize the functions of the two fibronectin type III (F3) homology domains of the neural cell adhesion molecule (NCAM), we investigated the effects of two variants, expressed as fusion proteins, of the NCAM-F3 domains on attachment and spreading of NCAM-expressing fibroblasts, cerebellar cell aggregation and fiber formation, and on growth cones. The two fusion proteins were different with regard to a short proline-rich insert of six amino acids between the two F3 domains. Immobilized NCAM-F3 fusion proteins were found to mediate attachment of both transmembrane and lipid-anchored NCAM expressing fibroblasts. Also NCAM-negative cells adhered to the NCAM-F3 substratum, although to a lesser extent, implying the possibility of a heterophilic ligand to NCAM-F3 domains on the surface of fibroblasts. Cellular spreading on NCAM-F3 substratum was selectively increased in fibroblasts expressing transmembrane NCAM, and only the NCAM-F3 fusion protein lacking the proline-rich insert was able to elicit this effect. Primary cultures of mouse cerebellum were strongly inhibited with regard to formation of cellular aggregates and fibers, when incubated in the presence of either of the two NCAM-F3 fusion proteins, the fusion protein with the proline-rich insert being the more effective one. Finally, the morphology of growth cones from rat cerebellar granule cells changed significantly when grown on NCAM-F3 substrata as revealed by computer-assisted image analysis. Thus, our data indicate that the NCAM-F3 domain are involved in cell-cell adhesion, and that insertion of the proline-rich sequence has a modulatory effect on NCAM-F3 domain functions.

Animals↗
PubMed1982

Radioautography of rat incisor dentin as a continuous record of the incorporation of a single dose of 3H-labeled proline and tyrosine.

After injection of labeled precursors such as 3H-proline or 3H-tyrosine into rats, the incisor dentin contains a continuous and stable record of precursor incorporation into labeled proteins. This record was visualized and quantitated with radioautography in order to evaluate the quantitative changes in enamel where newly secreted proteins randomize with older proteins and both are eventually lost. Up to 4 hours after injection, the pulse-dose was incorporated as a highly labeled band of predentin. The band was entirely within calcified dentin at 2 days and was further removed from new predentin by 4 and 8 days. Dentin which formed proximal to the heavily labeled band contained an amount of radioactivity reflecting the level of labeled precursor available at that time. A standardizing factor for experimental error was obtained by quantitating the reaction in the heavily labeled band, and a post-pulse incorporation factor was determined from the amount of radioactivity added per day as weakly labeled dentin. The variation within the heavily labeled band was assumed to reflect experimental error. The number of grains in the bands were averaged from 4 hours to 8 days to give the standardizing factor. This was multiplied by the ratio of enamel to dentin counts in the same section to obtain a corrected enamel count. In this way the coefficient of variation was improved from a high of 17.2% in uncorrected enamel counts to 2.4% in corrected counts. The post-pulse incorporation factor was higher with tyrosine than with proline. With proline it amounted to 5% increase per day from 1 to 4 days and 2.5% per day from 4 to 8 days after injection. In addition, with 3H-proline the incorporation into predentin increased from 30 minutes to 4 hours. With tyrosine, the counts increased from 30 minutes to 1 hour, but decreased by nearly one third from 1 to 4 hours. This was interpreted as a loss of short-lived matrix proteins including procollagen peptides produced during conversion from procollagen to tropocollagen in the predentin.

Animals↗
PubMed1990

Distribution of 3H-proline within transseptal fibers of the rat following release of orthodontic forces.

Maxillary right first molar teeth of rats were tipped mesially with an orthodontic appliance for 2 weeks (experimental group), 3H-proline was injected, and orthodontic forces were removed 6 hr later (time 0). The contralateral molar teeth of treated (internal control group) and age- and weight-matched untreated animals (external control group) were also studied. Diastemata were created between the molar teeth by the orthodontic appliance, and transseptal fibers between first and second (P less than 0.001) and second and third molars (P less than 0.005) were significantly lengthened as compared to external and internal controls at time 0. Diastemata between molar teeth were closed 5 days after removal of orthodontic force. Transseptal fibers adjacent to the source of the orthodontic force (mesial region) had the highest mean number of 3H-proline-labeled proteins at time 0 and at all times following removal of the force (P less than 0.001), and had the highest rate of labeled protein removal (P less than 0.001). Half-lives for removal of 3H-proline-labeled transseptal fiber proteins were significantly greater in mesial and distal regions and significantly less in middle regions of experimentals than in corresponding regions of external controls (P less than 0.001). These data suggest the following: 1) transseptal fibers adjust their length by rapid remodeling in regions experiencing a tensile force; 2) collagenous protein turnover within the middle third of the transseptal fibers is more rapid subsequent to release of orthodontic force than during normal physiologic drift, suggesting that this region adapts rapidly to changes in adjacent tooth position and that these fibers do not play a significant role in relapse of orthodontically relocated teeth; and 3) significant differences in turnover rates of 3H-proline-labeled transseptal ligament proteins of external and internal control quadrants suggest that tooth movement produces both local and systemic effects on collagenous protein metabolism.

Animals↗
PubMed2003

The structure of tri-proline in water probed by polarized Raman, Fourier transform infrared, vibrational circular dichroism, and electric ultraviolet circular dichroism spectroscopy.

Tripeptidesserve as model systems for understanding the so-called random-coil state of peptides and proteins. While it is well known that polyproline or proline-rich polypeptides adopt the very regular polyproline-II (PPII) or left-handed 3(1)-helix conformation, it was thus far not clear whether this is also the predominant structure adopted by proline-containing tripeptides. To clarify this issue, we have investigated the amide I' band profile in the ir, isotropic, and anisotropic Raman, and vibrational circular dichroism (VCD) spectrum of cationic and zwitterionic tri-proline in D(2)O. The data were analyzed by modifying a recently developed algorithm, which allows one to obtain the central dihedral angles of tripeptides from the amide I' band intensities (R. Schweitzer-Stenner, Biophysical Journal, 2002, Vol. 83, pp. 523-532). Our analysis revealed that the peptide adopts a nearly canonical PPII structure in water with psi and phi values in the range of 175 degrees -165 degrees and -70 degrees -(-80 degrees ), respectively. This is fully confirmed by the respective electronic ultraviolet-CD spectra. Our result indicates that the strong PPII propensity of trans proline results from local interactions between the pyrrolidine ring and the backbone and is not due to any long-range interactions.

Alanine↗
PubMed1990

Conformational studies on peptides with proline in the right-handed alpha-helical region.

The proline residues in proteins are known to play an important structural role. Recently, the role of a proline residue in the middle of right-handed alpha-helical segments of peptides has been the focus of attention. This role seems to be particularly important in the case of membrane proteins and in the tight packing of globular proteins. In the present study the right-handed alpha-helical region of the Ala-Pro dipeptide and of polypeptides containing this group have been investigated. Crystal structures of proline-containing alpha-helices from some proteins have been analyzed and energy minimization studies on some model fragments containing Ala-Pro in the right-handed alpha-helical conformation have been carried out using flexible geometry. The present calculations indicate that the right-handed alpha-helical region of conformational space is an energetically favored region that can also accommodate Ala-Pro in longer segments of right-handed alpha-helix. This is achieved due to minor variations in some of the internal parameters. Deviations in the backbone parameters of proline in the right-handed alpha-helix lead to a kink of about 23 degrees in the helix axis. These deviations have been characterized and a set of standard values has been suggested for producing such a kink. These values can be used for model building and as starting points for further minimization studies. Previous energy minimization studies have been done using rigid geometry. This may explain why the minimum for Ala-Pro in the right-handed alpha-helical region has not been recognized thus far.

Alcohol Dehydrogenase↗
PubMed1992

Minimum energy conformations of proline-containing helices.

Proline occurs frequently in transmembrane alpha-helices of transport and receptor proteins even though statistical surveys demonstrate the overwhelming preference of this residue for a non-alpha-helical, hydrophilic environment. As a result, membrane-buried proline has been proposed to be functionally important, with function arising from structural discontinuity or destabilization of the helix. Destabilization may occur by Pro-mediated conformational transitions between discrete states, and may be manifested in membrane protein systems through reversible processes such as channel opening and closing or signal transduction. In this study, computer modeling of a model transmembrane alpha-helix, (Ala)8-Leu-Pro-Phe-(Ala)8, in a medium of low polarity (dielectric = 2), is used to examine the occurrence and energetic accessibility of Pro-mediated conformational interconversions. Leu psi and chi 1, Pro psi, and Phe phi and chi 1 torsion angles were assigned random values so that a data base of 200 conformations for each of the cis and trans states was generated. The conformations were minimized and low-energy structures organized into families. This analysis demonstrated that the most populated lowest energy family is the Trans-I conformation, corresponding to proline in a kinked alpha-helix. Two additional trans structures, Trans-II and Trans-III, as well as a cis conformation, Cis-I, are also energetically competitive. Interconversions between the trans states could thus be mediated by changes at a single torsion angle, accompanied by minor local hydrogen-bonding rearrangements. This work substantiates that membrane-buried proline can provide the basis for conformational transitions between discrete alpha-helix-based structures in a nonpolar environment.

Amino Acid Sequence↗
PubMed1992

Some proline substituent effects in the tandem mass spectrum of protonated pentaalanine.

Tandem mass spectral effects of the replacement of alanine by proline in pentaalanine were studied. The principal difference when residue 3 or 4 is proline is the great enhancement of the y3 or y2 ion, respectively. This is precisely the principal difference which thermochemical arguments predict, since a y-type ion with N-terminal proline is estimated to be 32 kJ mol-1 more stable than with N-terminal alanine. When this proline effect and the effect of neutral diketopiperazine loss occur simultaneously, the y-type ion is not observed, as predicted from the additivity of substituent effects by the kinetic approach. No interpretation is offered for observations of b-type ion intensities, since the pattern is not obvious to us.

Alanine↗
PubMed2004

Cotranslational incorporation of a structurally diverse series of proline analogues in an Escherichia coli expression system.

A set of Escherichia coli expression strains have been defined that are competent for the incorporation of a structurally diverse series of proline analogues under culture conditions that are compatible with high levels of analogue substitution within a proline-rich protein substrate. These bacterial strains have been employed to assay the efficacy of incorporation of noncanonical amino acids into a recombinant-protein test substrate and to create variant polypeptides in which native protein sequences have been globally substituted with imino acid analogues in response to proline codons. We envision that these methods may be used to interrogate the effect of imino acid substitution on protein structure and function and may be particularly informative in the context of structural comparison of a series of modified proteins with respect to the stereoelectronic differences between the incorporated proline analogues.

Elastin↗
PubMed2003

Conformers of gaseous proline.

Accurate geometries, relative energies, rotational and quartic centrifugal distortion constants, dipole moments, harmonic vibrational frequencies, and infrared intensities were determined from ab initio electronic structure calculations for eighteen conformers of the neutral form of the amino acid L-proline. Only four conformers have notable population at low and moderate temperature. The second most stable conformer is only 2+/-2 kJ mol(-1) above the global minimum, while the third and fourth conformers are nearly degenerate and have an excess energy of 7+/-2 kJ mol(-1) relative to the global minimum. All four conformers have one hydrogen bond: N.HO in the lower energy pair of conformers, and NH.O in the higher energy pair of conformers. The conformer pairs differ only in their ring puckering. The relative energies of the conformers include corrections for valence electron correlation, extrapolated to the complete basis set limit, as well as core correlation and relativistic effects. Structural features of the pyrrolidine ring of proline are discussed by using the concept of pseudorotation. The accurate rotational and quartic centrifugal distortion constants as well as the vibrational frequencies and infrared intensities should aid identification and characterization of the conformers of L-proline by rotational and vibrational spectroscopy, respectively. Bonding features of L-proline, especially intramolecular hydrogen bonds, were investigated by the atoms-in-molecules (AIM) technique.

Algorithms↗
PubMed2002

Repair of oxidized purines and damaged pyrimidines by E. coli Fpg protein: different roles of proline 2 and lysine 57 residues.

The Escherichia coli Fpg protein is involved in the repair of oxidized purines, including the highly mutagenic 7,8-dihydro-8-oxoguanine (8-oxoG). The Fpg protein also excises various oxidized pyrimidines with high efficiency. We examined, by targeted mutagenesis, the role of two highly conserved amino acid residues, proline 2 (P2) and lysine 57 (K57), on the catalytic activities of the Fpg protein toward a ring-fragmentation product of thymine (alpha RT) and 5,6-dihydrothymine (dHT). The following E. coli mutant Fpg proteins were investigated: lysine 57 --> glycine (FpgK57G), proline 2 --> glycine (FpgP2G), and proline 2 --> glutamic acid (FpgP2E). The FpgK57G protein had barely detectable alpha RT and dHT-DNA glycosylase activities and produced minute amounts of a Schiff-base complex upon reaction with alpha RT containing DNA. In contrast, the activity of an FpgP2G mutant toward alpha RT was comparable to the wild type activity and produced a Schiff-base complex with this substrate. FpgP2E was completely inactive in all the assays, in contrast, to the other mutants. The crystal structure of a homologous Fpg protein from an extreme thermophile, Thermus thermophilus HB8, reveals that it is composed of two distinct domains connected by a flexible hinge (Sugahara et al. [2000]: EMBO J 19:3857-3869). The N-terminal proline, one primary residue for enzymatic catalysis, is positioned at the bottom of a cleft in close proximity to lysine 52 (analogous to K57 of the E. coli Fpg). Based on the biochemical assays, together with the crystal structure of T. thermophilus HB8 Fpg protein, we propose a two-nucleophile model for the enzymatic catalysis.

Catalytic Domain↗
PubMed2006

L-proline transport by purified cell types of lobster hepatopancreas.

The hepatopancreas of the American lobster, Homarus americanus, has four epithelial cell types that are anatomically distinguishable and can be separated for in vitro investigation of their individual biological roles in the intact organ using centrifugal elutriation. Previous studies employing this separation method have produced hepatopancreatic cell suspensions that have been used to examine the nature of copper transport, 2 Na+/1 H+ exchange, and D-glucose absorption by each cell type in isolation from the other cells comprising the tubular epithelium. The present investigation used this method to study amino acid transport by E-, F-, R-, and B-cells of the lobster hepatopancreas in order to characterize the absorption processes for protein digestion products by this organ and to identify which cell type was most likely the responsible agent for net transcellular transfer of these organic molecules from lumen to blood. Results indicated that heptopancreatic E- and F-cell types were the only cells exhibiting Na+-dependent 3H-L-proline transport. Further examination of 3H-L-proline influx by F-cell suspensions indicated that this cell type possessed plasma membrane Na+-dependent IMINO-like and B0-like transport mechanisms and Na+-independent L-like transport mechanisms. Using selective inhibitors of these separate transport systems (e.g., L-pipecolate, L-alanine, and L-leucine), the IMINO-like transporter appeared to predominate in L-proline influx into F-cells, while lesser amounts of amino acid transport took place by the B0-like and L-like systems. The results of this study suggest that the hepatopancreatic F-cell is the epithelial cell type responsible for the bulk of amino acid absorption by this organ and that the IMINO-like transporter is responsible for most of the L-proline transfer through this agent. It is further suggested that as digestion and absorption proceeds in the hepatopancreas and concentrations of luminal amino acids and sodium fall, Na+-dependent transport systems, like the IMINO-like and B0-like, increase their binding affinities for their substrates to maximize nutrient transfer across the epithelium.

Amino Acid Transport Systems, Neutral↗
PubMed2004

Synthesis of interkeratin matrix in differentiating lizard epidermis: an ultrastructural autoradiographic study after injection of tritiated proline and histidine.

During epidermal differentiation in mammals, keratins and keratin-associated matrix proteins rich in histidine are synthesized to produce a corneous layer. Little is known about interkeratin proteins in nonmammalian vertebrates, especially in reptiles. Using ultrastructural autoradiography after injection of tritiated proline or histidine, the cytological process of synthesis of beta-keratin and interkeratin material was studied during differentiation of the epidermis of lizards. Proline is mainly incorporated in newly synthesized beta-keratin in beta-cells, and less in oberhautchen cells. Labeling is mainly seen among ribosomes within 30 min postinjection and appears in beta-keratin packets or long filaments 1-3 h later. Beta-keratin appears as an electron-pale matrix material that completely replaces alpha-keratin filaments in cells of the beta-layer. Tritiated histidine is mainly incorporated into keratohyalin-like granules of the clear layer, in dense keratin bundles of the oberhautchen layer, and also in dense keratin filaments of the alpha and lacunar layer. The detailed ultrastructural study shows that histidine-labeling is localized over a dense amorphous material associated with keratin filaments or in keratohyalin-like granules. Large keratohyalin-like granules take up labeled material at 5-22 h postinjection of tritiated histidine. This suggests that histidine is utilized for the synthesis of keratins and keratin-associated matrix material in alpha-keratinizing cells and in oberhautchen cells. As oberhautchen cells fuse with subjacent beta-cells to form a syncytium, two changes occur : incorporation of tritiated histidine, but uptake of proline increases. The incorporation of tritiated histidine in oberhautchen cells lowers after merging with cells of the beta-layer, whereas instead proline uptake increases. In beta-cells histidine-labeling is lower and randomly distributed over the cytoplasm and beta-keratin filaments. Thus, change in histidine uptake somehow indicates the transition from alpha- to beta-keratogenesis. This study indicates that a functional stratum corneum in the epidermis of amniotes originates only after the association of matrix and corneous cell envelope proteins with the original keratin scaffold of keratinocytes.

Animals↗
PubMed1993

Use of proline mutants to help solve the NMR solution structure of type III antifreeze protein.

To help understand the structure/function relationships in antifreeze proteins (AFP), and to define the motifs required for ice binding, a Type III AFP suitable for two-dimensional (2D) NMR studies was produced in Escherichia coli. A synthetic gene for one of the Type III AFP isoforms was assembled in a T7 polymerase-directed expression vector. The 67-amino acid-long gene product differed from the natural AFP by inclusion of an N-terminal methionine but was indistinguishable in activity. The NMR spectra of this AFP were complicated by cis-trans proline isomerization from the C-terminal sequence YPPA. Substitution of this sequence by YAA eliminated isomer signals without altering the activity or structure of the mutant AFP. This variant (rQAE m1.1) was selected for sequential assignment and the secondary structure determination using 2D 1H NMR spectroscopy. Nine beta-strands are paired to form two triple-stranded antiparallel sheets and one double-stranded antiparallel sheet. Two further proline replacements, P29A and P33A, were made to delineate the role of conserved prolines in Type III AFP. These mutants were valuable in clarifying ambiguous NMR spectral assignments amongst the remaining six prolines of rQAE m1.1. In contrast to the replacement of the C-terminal prolyl residues, the exchange of P29 and P33 caused some structural changes and significantly decreased protein solubility and antifreeze activity.

Amino Acid Sequence↗
PubMed1993

Characterization of proline-containing alpha-helix (helix F model of bacteriorhodopsin) by molecular dynamics studies.

Many of the bilayer spanning segments of membrane transport proteins contain proline residues, and most of them are believed to occur in alpha-helical form. A proline residue in the middle of an alpha-helix is known to produce a bend in the helix, and recent studies have focused on characterizing such a bend at atomic level. In the present case, molecular dynamics (MD) studies are carried out on helix F model of bacteriorhodopsin (BR) Ace-(Ala)7-Trp-(Ala)2-Tyr-Pro-(Ala)2-Trp- (Ala)8-NHMe and compared with Ace-(Ala)7-Trp-(Ala)2-Tyr-(Ala)3-Trp-(Ala)8-NHMe in which the proline is replaced by alanine. The bend in the helix is characterized by structural parameters such as kink angle (alpha), wobble angle (theta), virtual torsion angle (rho), and the hydrogen bond distance d (Op-3 ... Np+1). The average values and the flexibility involved in these parameters are evaluated. The correlation among the bend related parameters are estimated. The equilibrium side chain orientations of tryptophan and tyrosine residues are discussed and compared with those found in the recently proposed model of bacteriorhodopsin. Finally, a detailed characterization of the bend in terms of secondary structures such as alpha I, alpha II and goniometric helices are discussed, which can be useful in the interpretation of the experimental results on the secondary structures of membrane proteins involving the proline residue.

Amino Acid Sequence↗
PubMed2006

Conformational studies of proline-, thiaproline- and dimethylsilaproline-containing diketopiperazines.

As proline plays an important role in biologically active peptides, many analogues of this residue have been developed to modulate the proportion of cis and trans conformers. A correlation between the pyrrolidine ring shape and structural properties of proline has been established. Diketopiperazine (DKP) is the model of choice to study the influence of the proline ring modification. In this contribution, cyclo(Gly-Pro) and two analogues cyclo(Sip-Pro) and cyclo(Thz-Pro) have been studied with proton NMR. We showed that both analogues with heteroatoms in gamma position, silicon and sulfur respectively, display a more rigid five-member ring. The usual flexibility of proline ring is restrained in both cases and only the two C(beta)-exo and C(beta)-endo conformations are observed.

Diketopiperazines↗
PubMed1996

An important role for pentose cycle in the synthesis of citrulline and proline from glutamine in porcine enterocytes.

This study was designed to determine a role of pentose cycle in the provision of NADPH for the synthesis of citrulline and proline from glutamine in porcine enterocytes. Enterocytes from 4-day-old pigs were incubated at 37 degrees C for 0 to 30 min in Krebs-Henseleit bicarbonate buffer (pH 7.4) containing 2 mM glutamine and 5 mM glucose in the presence of 0, 0.1, or 0.25 mM dehydroepiandrosterone (DHEA), a potent inhibitor of glucose-6-phosphate dehydrogenase which is the key regulatory enzyme of pentose cycle. The activity of this cycle was estimated with the use of [1-14C]glucose and [6-14C]glucose. In some experiments, the medium included 2 mM ornithine and 2 mM NH4Cl (no glutamine). About 14% of glucose taken up by enterocytes was metabolized via pentose cycle. The flux from glucose into this cycle was decreased by 70 and 86%, respectively, in the presence of 0.1 and 0.25 mM DHEA compared with its absence. DHEA inhibited the synthesis of ornithine, citrulline, arginine, and proline from glutamine in a concentration-dependent manner, but had no effect on the formation of citrulline and arginine from ornithine. However, DHEA decreased the synthesis of proline from ornithine by 79%. DHEA had no effect on cellular ATP concentrations. These results provide the first line of evidence suggesting that glucose metabolism via pentose cycle plays an important role in providing NADPH for the conversion of glutamine into pyrroline-5-carboxylate in porcine enterocytes, which may explain the glucose-dependent synthesis of citrulline and proline from glutamine in these cells.

Adenosine Triphosphate↗