What is the role of Phosphatidyl Serine in the methylation protocols?

I'm following Dr Sarah Myhill's Methylation Protocol which includes Phosphatidyl Serine but I'd like to understand how it aids the methylation protocols. She advocates taking two a day but it is very expensive, and obviously I will start low and slow anyway.

I have already bought some and I'd like to know what to expect when taking it - more or less detox/die off/low potassium or other nasty side effects?

TIA :)