I actually know the answer to that. They dont!
Glut and protein do completely different things. Actually, muscle protein is MADE of glutamine in our bodies. So during muscle synthesis our body calls on the food we eat for the glut so that they can build. The philosophy goes the less glut we have the longer it takes to build muscle!
I will tell you this however, different types of proteins have different absorption rates in our bodies. And to help increase this number take a few grams of ginger a day. ALSO, dont buy cheap protein. It is cheap because its absorption rate in our body is really low (ie you get stomach pains). Get good protein like myoplex, metrx, or isopure.
bottom line - glut is an Amino Acid that is needed to help repair muscle tissue (along with glycine, alanine, valine, leucine, and isoleucine). protein is the backbone to this synthesis but BOTH are need for optimal growth!
MM