Phosphatidate phosphohydrolase in purified rat brain myelin

Vaswani, Kuldeep K.; Ledeen, Robert W.

doi:10.1002/jnr.490240313

Cited by 5 publications

(2 citation statements)

References 46 publications

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“…In brain and liver microsomal fractions from adult rats, the PAP 2 form was higher than the PAP 1 form. In this respect, it has been demonstrated that highly-puri®ed myelin from rat brain stem contains PAP 2 and that it is intrinsic to myelin membranes (Vaswani and Ledeen, 1989).…”

Section: Discussionmentioning

confidence: 99%

Aging promotes a different phosphatidic acid utilization in cytosolic and microsomal fractions from brain and liver

Pasquaré

Boschero

Giusto

2001

Experimental Gerontology

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Section: Discussionmentioning

confidence: 99%

Aging promotes a different phosphatidic acid utilization in cytosolic and microsomal fractions from brain and liver

Pasquaré

Boschero

Giusto

2001

Experimental Gerontology

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“…In addition, at least in our hands, the diolein used for preparation of the substrate, and the unlabeled dioleoyl-containing phosphatidate used to dilute the radioactive substrate are more easily dispersed than the corresponding palmitoyl species. Furthermore, the activities of some isozymes of PAP have been reported to be higher when measured by determination of phosphate released from dioleoyl-phosphatidate as compared to dipalmitoyl-phosphatidate (e.g., [15][16][17][18]. Confirming this, using both the diacylglycerol-and the phosphate determination method, we have found the activity of rat liver cytosolic PAP, purified by hydroxylapatite chromatography, to be 2-2.5-fold higher with dioleoyl-phosphatidate than with the dipalmitoyl substrate.…”

Section: Resultsmentioning

confidence: 99%

Difficulties in the assay of phosphatidate phosphohydrolase activity. Influence of ionic strength, detergent, and selection of substrate

Stark

Humble

1996

Lipids

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In the present paper, problems in connection with assay of the activity of magnesium-dependent rat liver phosphatidate phosphohydrolase (PAP) are discussed. PAP activity is usually measured by following the production of diacylglycerol or inorganic phosphate from the substrate phosphatidate. These two methods may give widely different results due to a number of factors that may affect the assay. One such factor is the composition of the substrate. Higher apparent enzyme activity was observed with dioleoyl-phosphatidate than with dipalmitoyl-phosphatidate. This substrate-dependent difference in apparent PAP activity was 2-2.5-fold in the absence and 10-fold in the presence of Triton X-100, respectively. Triton X-100 reduced the activity as measured with the dipalmitoyl-phosphatidate substrate. In contrast, the activity of PAP as measured with dioleoyl-phosphatidate was stimulated by Triton X-100. The stimulatory effect of Triton was reduced or abolished when the ionic strength in the assay mixture was increased. Assays based on 32P-labeled substrate are rapid and sensitive. It is shown here that 33P can be used as an alternative. This radionuclide has a longer half-life and also emits particles with lower energy, thus posing less potential health hazards for the user.

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Axon-myelin transfer of phospholipids and phospholipid precursors

1992

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Previous studies have provided evidence for axon-to-myelin transfer of intact lipids and lipid precursors for reutilization by myelin enzymes. Several of the lipid constituents of myelin showed significant contralateral/ipsilateral ratios of incorporated radioactivity, indicative of axonal origin, whereas proteins and certain other lipids did not participate in this transfer-reutilization process. The present study will examine the labeling of myelin phosphoinositides by this pathway. Both 32PO4 and [3H]inositol were injected monocularly into 7-9-wk-old rabbits and myelin was isolated 7 or 21 days later from pooled optic tracts and superior colliculi. In total lipids 32P counts of the isolated myelin samples showed significant contralateral/ipsilateral ratios as well as increasing magnitude of contralateral-ipsilateral differences during the time interval. Thin-layer chromatographic isolation of the myelin phosphoinositides revealed significant 32P-labeling of these species, with PIP and PIP2 showing time-related increases. This resembled the labeling pattern of the major phospholipids from rabbit optic system myelin in a previous study and suggested incorporation of axon-derived phosphate by myelin-associated enzymes. The 32P label in PI, on the other hand, remained constant between 7 and 21 days, suggesting transfer of intact lipid. This was supported by the labeling pattern with [3H]inositol, which also showed no increase over time for PI. These results suggest axon-myelin transfer of intact PI followed by myelin-localized incorporation of axon-derived phosphate groups into PIP and PIP2. The general topic of axon-myelin transfer of phospholipids and phospholipid precursors is reviewed.

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Phosphatidate phosphohydrolase in purified rat brain myelin

Cited by 5 publications

References 46 publications

Aging promotes a different phosphatidic acid utilization in cytosolic and microsomal fractions from brain and liver

Aging promotes a different phosphatidic acid utilization in cytosolic and microsomal fractions from brain and liver

Difficulties in the assay of phosphatidate phosphohydrolase activity. Influence of ionic strength, detergent, and selection of substrate

Axon-myelin transfer of phospholipids and phospholipid precursors

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