Table 1.
Some of the constituents of myelin and their relative distribution (assembled from information in [2, 48, 170–175]).
| Constituent | CNS myelin | PNS myelin |
|---|---|---|
| Myelin proteins (make up 20–30% w/w of myelin) | ||
| Myelin proteolipid protein (PLP)/DM20 | >50%* (PLP > DM20) |
0.05% (DM20 > PLP)† |
| Myelin basic protein (MBP, also known as P1) | 30% | 5–15%†† |
| Oligodendrocyte-specific protein (OSP) | 7% | Not detected |
| 2′,3′-Cyclic-nucleotide 3′-phosphodiesterase (CNPase) | 2–4% | 0.2% |
| Myelin associated glycoprotein (MAG) | 1% | 0.1% |
| Myelin oligodendrocyte glycoprotein (MOG) | 0.01–0.05% | Not detected |
| P0 (glycoprotein) | Not detected | 50% |
| P2 | <0.01% | 5–10%†† |
| PMP22 | <0.01% | 5–10%†† |
| Myelin lipids (make up 70–80% of total dry weight of myelin) | ||
| Galactocerebroside (GalC) | 23% | ~10% |
| Sulphatide | 4% | ~2% |
| Gangliosides | 0.1–0.3% | ~0.1%¶ |
*Percentages represent the proportion of the molecule within the whole class of molecule; for example, >50% of the total protein fraction is PLP
†PLP and DM20, the alternatively spliced isoform of PLP, are present at very low concentrations in Schwann cells, but are not inserted into the PNS myelin membrane.
††Amounts vary depending on the peripheral nerves used as a source of tissue.
¶One of the most abundant gangliosides in human PNS myelin is LM1, which is not present in CNS myelin.