Here is a link to protein matabilizm and how glucose is manufactured from protein. The part most interesting is:

http://www.unisanet.unisa.edu.au/08366/h%26p2ptn.htm

Gluconeogenesis
The process of conversion of lactate to glucose is called gluconeogenesis, uses some of the reactions of glycolysis (but in the reverse direction) and some reactions unique to this pathway to re-synthesise glucose. This pathway requires an energy input (as ATP) but has the role of maintaining a circulating glucose concentration in the bloodstream (even in the absence of dietary supply) and also maintaining a glucose supply to fast twitch muscle fibres.
Seems like your body will only produce enough glucose from protein to maintain a supply for fast twich muscle fibres.