To put it simply, glucose contains elements such as C, H, O, while protein generally contains elements such as C, H, O, N, S, P, etc., so it can't.

Here, the three substances in the human body can be transformed into each other. Sugar and fat can be transformed into each other. The conversion of fat into amino acids is limited (not all fats can be converted into amino acids). Amino acids can be converted into fat and sugar, but sugar cannot be converted into amino acids.