Cholesterol biosynthesis in Zellweger syndrome: Normal activity of mevalonate kinase, mevalonate‐5′‐pyrophosphate decarboxylase and IPP‐isomerase in patients' fibroblasts but deficient mevalonate kinase activity in liver

Wanders, Ronald J. A.; Romeijn, G. J.

doi:10.1007/bf01799427

Cited by 16 publications

(9 citation statements)

References 13 publications

(7 reference statements)

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“…In view of these results, we employed a more focused experimental approach that utilizes the ample sequence data available for mevalonate kinases from a variety of diverse species. Although human mevalonate kinase contains 41 carboxylate residues, comparison of this sequence to those of the protein from Rattus norvegicus (30), Arabidopsis thaliana (31), Saccharomyces cerevisiae (32), Schizosaccharomyces pombe, 4 and Methanobacterium thermoautotrophicum 5 indicated only four invariant carboxylates (Fig. 3), which include three glutamic acids (Glu-19, Glu-193, and Glu-296) and one aspartic acid (Asp-204).…”

Section: Isolation Of Human Mevalonatementioning

confidence: 99%

“…The enzyme has long been considered to be a cytosolic protein, but recent work on mevalonate kinase has implicated it in peroxisomal metabolism (3). In this context, depressed mevalonate kinase activity has also been correlated with peroxisomal deficiency disorders (4,5). Although these observations suggest that detailed information on this enzyme would be useful, mevalonate kinase has not received as much attention as other enzymes in the isoprenoid/sterol biosynthetic pathway.…”

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confidence: 99%

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Identification of Catalytic Residues in Human Mevalonate Kinase

Potter¹,

Miziorko

1997

Journal of Biological Chemistry

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cDNA encoding human mevalonate kinase has been overexpressed and the recombinant enzyme isolated. This stable enzyme is a dimer of 42-kDa subunits and exhibits a V m ‫؍‬ 37 units/mg, K m(ATP) ‫؍‬ 74 M, and K m(DL-MVA) ‫؍‬ 24 M. The sensitivity of enzyme to watersoluble carbodiimide modification of carboxyl groups prompted evaluation of four invariant acidic amino acids (Glu-19, Glu-193, Asp-204, and Glu-296) by site-directed mutagenesis. Elimination of Glu-19's carboxyl group (E19A, E19Q) destabilizes the enzyme, whereas E19D is stable but exhibits only ϳ2-fold changes in V m and K m values. E296Q is a stable enzyme, which exhibits kinetic parameters comparable to those measured for wild-type enzyme. E193A is a labile protein, whereas E193Q is stable, exhibiting >50-fold diminution in V m and elevated K m values for ATP (ϳ20-fold) and mevalonate (ϳ40-fold). Such effects would be compatible with a role for Biosynthesis of isoprenoids and sterols requires the ATP-dependent phosphorylation of mevalonic acid. In humans, diminished activity of mevalonate kinase (EC 2.7.1.36), the enzyme that catalyzes this reaction (1), results in mevalonic aciduria (2). The enzyme has long been considered to be a cytosolic protein, but recent work on mevalonate kinase has implicated it in peroxisomal metabolism (3). In this context, depressed mevalonate kinase activity has also been correlated with peroxisomal deficiency disorders (4, 5). Although these observations suggest that detailed information on this enzyme would be useful, mevalonate kinase has not received as much attention as other enzymes in the isoprenoid/sterol biosynthetic pathway.Enzymological characterization of mammalian mevalonate kinase has included kinetic work (6), which suggests that the enzyme catalyzes an ordered sequential reaction with mevalonic acid assigned as the first substrate bound and phosphomevalonate as the first product released. Inhibition of the enzyme by geranyl pyrophosphate (7) and farnesyl pyrophosphate (8), metabolites that are formed downstream in the isoprenoid biosynthetic pathway, has been reported, and such inhibition has been suggested to have physiological relevance (9, 10). Although an amino acid substitution that presumably accounts for human mevalonic aciduria has been documented (11), little is known about the active site amino acids that are important to enzyme function. Group-specific reagents have been employed to demonstrate that mevalonate kinase contains reactive cysteine (6) and lysine (12) residues. Recently, the first identification of an active site amino acid was accomplished when protein chemistry and mutagenesis work indicated that lysine-13 influences ATP binding (13).Availability of a recombinant form of human mevalonate kinase would facilitate studies on inherited mutations in this enzyme. Such an enzyme, available in a stable, highly purified form and in substantial amounts, could also be useful for investigation of the structure/function correlations that account for phosphomevalonate production or for feedbac...

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Section: Isolation Of Human Mevalonatementioning

confidence: 99%

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confidence: 99%

Identification of Catalytic Residues in Human Mevalonate Kinase

Potter¹,

Miziorko

1997

Journal of Biological Chemistry

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“…1219, PG I-228, 1993), two other studies showed that cholesterol biosynthesis rates were equivalent to or slightly higher than those in control fibroblasts (33,37). A study by Krisans et al (31) analyzing liver samples from Zellweger spectrum patients has shown that enzymatic activities of HMG-CoA reductase, MvK, phosphomevalonate kinase, MPD, IPPI, and FPP synthase were reduced, while another group reported decreased or normal MvK activities in livers of ZS patients (54). In addition, one group reported a decrease in cholesterol biosynthesis in peroxisome-deficient PEX2 Ϫ/Ϫ hamster cells (1), while another group reported increased cholesterol biosynthesis in the same cell lines (52).…”

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confidence: 97%

“…Briefly, reduced plasma cholesterol levels have been found in Zellweger spectrum patients (30). Normal enzyme activities for mevalonate kinase (MvK), mevalonate diphosphate decarboxylase (MPD), and isopentenyl diphosphate isomerase (IPPI) have been measured in fibroblasts from ZS patients in one study (54), but decreased MvK activity was found in fibroblasts from ZS and neonatal adrenoleukodystrophy patients in another study (6). While three groups reported significantly decreased cholesterol biosynthesis in fibroblasts from Zellweger spectrum patients (25,34; J. C. Collins, F. Keyserman, S. C. Rumsey, and R. J. Deckelbaum, Am.…”

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Disturbed Cholesterol Homeostasis in a Peroxisome-Deficient PEX2 Knockout Mouse Model

Kovacs

Shackelford

Tape

et al. 2004

Molecular and Cellular Biology

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We evaluated the major pathways of cholesterol regulation in the peroxisome-deficient PEX2 ؊/؊ mouse, a model for Zellweger syndrome. Zellweger syndrome is a lethal inherited disorder characterized by severe defects in peroxisome biogenesis and peroxisomal protein import. Compared with wild-type mice, PEX2 ؊/؊ mice have decreased total and high-density lipoprotein cholesterol levels in plasma. Hepatic expression of the SREBP-2 gene is increased 2.5-fold in PEX2 ؊/؊ mice and is associated with increased activities and increased protein and expression levels of SREBP-2-regulated cholesterol biosynthetic enzymes. However, the upregulated cholesterogenic enzymes appear to function with altered efficiency, associated with the loss of peroxisomal compartmentalization. The rate of cholesterol biosynthesis in 7-to 9-day-old PEX2 ؊/؊ mice is markedly increased in most tissues, except in the brain and kidneys, where it is reduced. While the cholesterol content of most tissues is normal in PEX2 ؊/؊ mice, in the knockout mouse liver it is decreased by 40% relative to that in control mice. The classic pathway of bile acid biosynthesis is downregulated in PEX2 ؊/؊ mice. However, expression of CYP27A1, the rate-determining enzyme in the alternate pathway of bile acid synthesis, is upregulated threefold in the PEX2 ؊/؊ mouse liver. The expression of hepatic ATP-binding cassette (ABC) transporters (ABCA1 and ABCG1) involved in cholesterol efflux is not affected in PEX2 ؊/؊ mice. These data illustrate the diversity in cholesterol regulatory responses among different organs in postnatal peroxisomedeficient mice and demonstrate that peroxisomes are critical for maintaining cholesterol homeostasis in the neonatal mouse.

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“…At least one missense mutation (N301T) has been documented as the cause of the disease in the index patient (3). Recently, diminished mevalonate kinase activity has been implicated in a second disorder of sterol metabolism, Zellweger syndrome (4). However, the molecular basis for the decreased mevalonate kinase activity associated with this disease remains to be elucidated.…”

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Identification and Functional Characterization of an Active-site Lysine in Mevalonate Kinase

Potter¹,

Wojnar

Narasimhan

et al. 1997

Journal of Biological Chemistry

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Mevalonate kinase (EC 2.7.1.36) catalyzes the transfer of the ␥-phosphoryl group of ATP to the C-5 hydroxyl oxygen of mevalonic acid (1) to produce a key intermediate in the pathways for biosynthesis of polyisoprenoids and sterols. Recently, the significance of this enzyme has been elevated by the documentation of defects that arise when production of 5-phosphomevalonate is either diminished or elevated from the usual physiological range. Mevalonic aciduria is an inherited metabolic disease that results from diminished mevalonate kinase activity in infants and children (2). At least one missense mutation (N301T) has been documented as the cause of the disease in the index patient (3). Recently, diminished mevalonate kinase activity has been implicated in a second disorder of sterol metabolism, Zellweger syndrome (4). However, the molecular basis for the decreased mevalonate kinase activity associated with this disease remains to be elucidated. In contrast, human hepatocytes that overexpress mevalonate kinase as a result of insertional activation by hepatitis B virus have an increased rate of cellular transformation. Presumably, this results from changes in prenylation of hepatocyte signal transduction effectors (5). While the above observations suggest that a detailed understanding of the factors that modulate production of 5-phosphomevalonate would be desirable, mevalonate kinase has been subjected to far less scrutiny than other enzymes in the pathway for polyisoprenoid and sterol biosynthesis.Kinetic studies (6) suggest that mevalonate kinase catalyzes an ordered sequential reaction; mevalonic acid is the first substrate bound, and phosphomevalonate is the first product released. The downstream products of the polyisoprenoid pathway, farnesyl pyrophosphate and geranyl pyrophosphate are potent competitive inhibitors of mevalonate kinase with respect to ATP (7). The enzyme has been reported to contain reactive cysteine (6) and lysine (8) residues. However, despite the recent elucidation of cDNA sequences for mevalonate kinase from a variety of species, the identity and functional significance of those reactive amino acids remain to be determined.Availability of a recombinant form of the enzyme would facilitate studies aimed at elucidation of the structure/function correlations that account for the reaction catalyzed by mevalonate kinase as well as for the features responsible for feedback inhibition. Using cDNA that encodes rat mevalonate kinase (9), we have developed a bacterial expression system that allows overexpression and facile isolation of the enzyme. The utility of this recombinant model system is illustrated by a series of experiments that account for the first identification and functional assignment of a mevalonate kinase active-site amino acid. A summary of a portion of this work has recently appeared (10). EXPERIMENTAL PROCEDURES MaterialsThe pGR50 plasmid harboring the full-length (1286 base pairs) cDNA that encodes rat mevalonate kinase was a gift from the BristolMyers Squibb Co. Restriction end...

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Cholesterol biosynthesis in Zellweger syndrome: Normal activity of mevalonate kinase, mevalonate‐5′‐pyrophosphate decarboxylase and IPP‐isomerase in patients' fibroblasts but deficient mevalonate kinase activity in liver

Cited by 16 publications

References 13 publications

Identification of Catalytic Residues in Human Mevalonate Kinase

Identification of Catalytic Residues in Human Mevalonate Kinase

Disturbed Cholesterol Homeostasis in a Peroxisome-Deficient PEX2 Knockout Mouse Model

Identification and Functional Characterization of an Active-site Lysine in Mevalonate Kinase

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