Characterization of phospholipid methylation in rat brain myelin

Abstract

Highly purified rat brain myelin was solubilized in Triton X-100 and myelin phospholipid N-methyltransferase was characterized. The enzyme activities were separated by isoelectric focusing and ion-exchange chromatography. The phospholipid methyl-transferase has shown at least four peaks of activity with pIapp. values of 4.5, 5.2, 6.2 and 8.4. After affinity purification each of these activities revealed a close set of bands of approx. 65 kDa on SDS/PAGE. These data together with those from preparative SDS/PAGE separations suggested that rat brain myelin contains three acidic and at least one basic phospholipid-methylating isoenzymes and that the major isoenzyme in each case is approx. 65 kDa in size. While the predominant product of the reaction catalysed by all detected isoforms was monomethylated phosphatidylethanolamine, the least acidic isoform (pIapp. 6.2) also formed about 20% phosphatidylcholine, suggesting that these isoenzymes may play different roles in vivo.

Short Stature Caused by a Mutant Growth Hormone

“…12 Serum samples (200 to 300 m l) were electrofocused in a buffer containing 1 percent hydroxypropyl methylcellulose and 4 percent ampholine (pH gradient, 3.5 to 8.0) at 200 V for 12 hours and then at 500 V for 12 hours. The fractions were collected and assayed for immunoreactive growth hormone.…”

Relationships Between Phosphatidylcholine, Phosphatidylethanolamine, and Sphingomyelin Metabolism in Cultured Oligodendrocytes

“…Therefore, and because PE methylation is the sole pathway of net choline synthesis, the PE methylation activity by oligodendrocytes in vivo might be higher. Also, the activity of PEMT may play a role in the maintenance of the myelm structure (Tsvetnitsky et al, 1995). This view is supported by the observation that a decreased level of S-adenosyl-L-methionine is associated with demyelination (Bottiglieri et al, 1994).…”

“…One should keep in mind that brain is a very heterogeneous tissue and that possibly some of the cells in the CNS, i.e., oligodendrocytes, might be relatively enriched in PEMT activity. Indeed, it has been shown (Dainous et al, 1982) that the PE methylation activity is much higher in glial cells than in neurons and that PBMT activity is intrinsic to myelin (Tsvetnitsky et al, 1995). Choline reuptake by neurons after neurotransmission is highly efficient, and thus the amounts of extracellular choline available for oligodendrocytes might be limited.…”

Short stature in two siblings heterozygous for a novel bioinactive GH mutant (GH-P59S) suggesting that the mutant also affects secretion of the wild-type GH

“…After 24-h incubation, cells were stimulated with 50 mM forskolin (Sigma-Aldrich) for an additional 24 h when aliquots of culture medium were collected. Isoelectric focusing was performed as described (25). Patient serum or culture media samples (200-300 ml) were electrofocused in a buffer containing 1% hydroxypropyl methylcellulose and 4% ampholine (pH gradient, 3.5-8.0) at 200 V for 12 h and then at 500 V for 12 h. The fractions were collected and assayed for immunoreactive GH.…”