Clarification about how proteomics data is considered in ftINIT

[nnursimulu]

Dear code developers and maintainers,

I am interested in performing metabolic reconstruction using ftINIT and proteomics data. However, I am afraid I am finding little guidance for this. Could you please help me out? In particular,

1. I did find that for making reconstructions using Human Protein Atlas data, I first need to process the data using the function parseHPA. I downloaded sample information from the Human Protein Atlas; however the function appears to rely on the existence of a column called "Expression type". This appears missing in my downloads. Can you please clarify what value this should take?
2. The level of expression ("Level") appears to be one from a set of well-defined values: "Medium", "High", "Low" for instance. Is this relative to the abundance of other proteins in the same sample?
3. Can you please direct me to a resource which explains how the discrete values (as mentioned in 2) are utilized in metabolic reconstruction?

I would be very grateful for your help!