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Biomedical subjects

L J Goad

Publications and source records attributed to L J Goad.

At least 55 records · Page 3Linked to original sources
PubMed1973

S-adenosyl-L-methionine-cycloartenol methyltransferase activity in cell-free systems from Trebouxia sp. and Scenedesmus obliquus.

1. Homogenates prepared from Trebouxia sp. 213/3 and Scenedesmus obliquus exhibited S-adenosyl-l-methionine-cycloartenol methyltransferase activity. 2. The products of the reaction, with cycloartenol as the substrate, were 24-methylenecycloartanol and cyclolaudenol. 3. Optimal enzyme activity was found in homogenates prepared at pH7.6 and the transmethylase was distributed between the supernatant and microsomal fractions of the Trebouxia homogenate. 4. The relevance of these results is discussed in relation to C(28) and C(29) sterol production in the algae.

Carbon Radioisotopes↗
PubMed1969

Incorporation of (2-14C, (5r)-5-3H1) mevalonic acid into cholesterol by a rat liver homogenate and into beta-sitosterol and 28-isofucosterol by larix decidua leaves.

1. Incubation of a rat liver homogenate with 3R-[2-(14)C,(5R)-5-(3)H(1)]mevalonic acid gave cholesterol with (3)H/(14)C atomic ratio 6:5. 2. Conversion of the labelled cholesterol into 3beta-acetoxy-6-nitrocholest-5-ene or cholest-4-ene-3,6-dione resulted in the loss of one tritium atom from C-6. 3. These results show that during cholesterol biosynthesis the 6alpha-hydrogen atom of a precursor sterol is eliminated during formation of the C-5-C-6 double bond. 4. Incorporation of 3R-[2-(14)C,(5R)-5-(3)H(1)]mevalonic acid into the sterols of larch (Larix decidua) leaves gave labelled cycloartenol and beta-sitosterol with (3)H/(14)C atomic ratios 6:6 and 6:5 respectively. 5. One tritium atom was lost from C-6 on conversion of the labelled beta-sitosterol into either 3beta-acetoxy-6-nitrostigmast-5-ene or stigmast-4-ene-3,6-dione, demonstrating that formation of the C-5-C-6 double bond of phytosterols also involves the elimination of the 6alpha-hydrogen atom of a precursor sterol. 6. The 3R-[2-(14)C,(5R)-5-(3)H(1)]mevalonic acid was also incorporated by larch (L. decidua) leaves into a sterol that co-chromatographed with 28-isofucosterol. Confirmation that the radioactivity was associated with 28-isofucosterol was obtained by co-crystallization with carrier 28-isofucosterol and ozonolysis of the acetate to give radioactively labelled 24-oxocholesteryl acetate. 7. The significance of these results to phytosterol biosynthesis is discussed.

Animals↗