Isolation of a Stearoyl CoA Desaturase from <i>Tetrahymena thermophila</i>

Bertram, Jon; Erwin, Joseph A.

doi:10.1111/j.1550-7408.1981.tb02818.x

Cited by 3 publications

(1 citation statement)

References 30 publications

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“…Cholesterol desaturases from Tetrahymena require reduced cofactors, molecular oxygen, CYT b 5 , and eventually also phospholipids. These features are shared by other desaturases, such as fatty acid desaturases present in the same organism (Bertram and Erwin 1981; Sasaki et al 1984), 4‐methyl sterol oxidase (Fukushima et al 1983), and lathosterol 5‐desaturase of various sources (Ishibashi 2002). …”

Section: Discussionmentioning

confidence: 99%

Characterization and Properties of Cholesterol Desaturases from the Ciliate Tetrahymena thermophila

Nusblat

Muñoz

Valcarce³

et al. 2005

J Eukaryotic Microbiology

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Live Tetrahymena thermophila transforms exogenous cholesterol into 7,22-bis, dehydrocholesterol (DHC) by desaturation at positions C7(8) and C22(23) of the cholesterol moiety. In this first report on expression, isolation, characterization, and reconstitution of Tetrahymena's cholesterol desaturases in cell-free extracts, we describe conditions for increasing the expression of both desaturases based on the addition of specific sterols to the culture medium. Reactions performed in vitro, with isolated microsomes, yield only the mono-unsaturated derivatives, 7-DHC and/or 22-DHC. However, selectivity towards one product can be improved with the addition of specific compounds: beta-mercaptoethanol inhibited C22(23) desaturase activity completely, while ethanol selectively increased this activity. Detergent-solubilized microsomes showed no desaturase activity, but partial restoration could be achieved with addition of dilauroyl-phosphatidylcholine liposomes (25%). Both cholesterol desaturases require molecular oxygen and cytochrome b(5). NADH or NADPH can serve as reduced cofactors, albeit with different efficiency, delivered by reductases present in the microsomal fraction. Azide and cyanide, but not azole compounds, inhibited these desaturases, suggesting a key role for cytochrome b(5) in these reactions.

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Section: Discussionmentioning

confidence: 99%

Characterization and Properties of Cholesterol Desaturases from the Ciliate Tetrahymena thermophila

Nusblat

Muñoz

Valcarce³

et al. 2005

J Eukaryotic Microbiology

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Isolation of a Δ 7 -cholesterol desaturase from Tetrahymena thermophila

Valcarce

Florin‐Christensen²,

Nudel

2000

Applied Microbiology and Biotechnology

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Cell-free preparations of Tetrahymena thermophila catalyze the direct desaturation of cholesterol to delta7-dehydrocholesterol (provitamin D3). The activity was isolated in the microsomal fraction from Tetrahymena homogenates. Delta7-desaturase activity was stimulated fivefold by the addition of 6 mM ATP. Other cofactors assayed, including NAD, NADP, NADH or NADPH, had no significant effect. The activity was found in microsomes prepared from stationary-phase cultures of the ciliate, grown either with or without added cholesterol, thus indicating that it is constitutively expressed in T. thermophila cells.

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The Effect of Dietary Sterol on the Activity of Fatty Acid Desaturases Isolated from Tetrahymena setosa

Koll

Erwin

1990

The Journal of Protozoology

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Tetrahymena setosa has a nutritional requirement for micro amounts of sterol, a requirement which is also satisfied by relatively large amounts of either intact phospholipids or a mixture of unsaturated fatty acids normally found in these ciliates. Three microsomal fatty acyl-CoA desaturases have been isolated from T. setosa and partially characterized. These enzymes which can account for the formation of the majority of the ciliate's unsaturated fatty acids, include: a delta 9, a delta 12 and a delta 6 desaturase which catalyze the transformation of stearoyl-CoA to oleic acid, of oleoyl-CoA to linoleic acid and of linoleoyl-CoA to gamma-linolenic acid, respectively. The stearoyl CoA desaturase required NAD (or NADP), ATP and free CoA; the delta 6 and delta 12 desaturases required NADP, but not ATP or CoA. Cellular levels of the three desaturases were highest in mid-logarithmic phase cells and lowest in stationary phase cells. In order to determine if there was a relationship between the sterol requirement and the ability of the organism to desaturate, T. setosa was grown in a synthetic medium supplemented with either cholesterol or a phospholipid which permits growth in the absence of cholesterol, or with both phospholipid and cholesterol. Cells grown with phospholipid alone had only half as much stearoyl-CoA and oleoyl-CoA desaturase activity as cells of identical culture age grown either on cholesterol alone or on cholesterol plus phospholipid.

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Isolation of a Stearoyl CoA Desaturase from Tetrahymena thermophila

Cited by 3 publications

References 30 publications

Characterization and Properties of Cholesterol Desaturases from the Ciliate Tetrahymena thermophila

Characterization and Properties of Cholesterol Desaturases from the Ciliate Tetrahymena thermophila

Isolation of a Δ 7 -cholesterol desaturase from Tetrahymena thermophila

The Effect of Dietary Sterol on the Activity of Fatty Acid Desaturases Isolated from Tetrahymena setosa

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