Glycine?? You're kidding, right? It's the simpliest AA of them all. It's not even an 'essential' AA, as your body can make it from any of the other ones. Plus, I can't believe that you 'burn' individual AA's. Your energy output is first from Carbohydrates (via the Kreb's cycle), then from stored fat, then from proteins (the ketosis thing that KtG mentioned is the 'ketones' from the AA's turning up in your urine, a sign that you're starving and burning protein).
Why yes I did take a graduate course or two in biochemistry (including nutritional biochemistry), now that you mention it.
It's Amino world without Chemists