ʟ-Glutamine solubility in hot water
Glutamine in aqueous solutions degrades slowly when stored in room temperature. Therefore, we can expect that rate of degradation is faster at higher temperatures. It is evident that the hydrolysis product of glutamine is 5-pyrrolidone-2-carboxylic acid (not glutaric acid as shown for enzymatic degradation) and ammonia (Ref.1):

The Ref.1 states that:

The degradation kinetics of ʟ-glutamine (Gln) in aqueous solution was studied as a function of buffer concentration, $\mathrm{pH}$ and temperature. Stability tests were performed using a stability-indicating high-performance liquid chromatographic assay. The degradation product of Gln was 5-pyrrolidone-2-carboxylic acid. The reaction order for Gln in aqueous solution followed pseudo-first-order kinetics under all experimental conditions. The maximum stability of Gln was observed in the $\mathrm{pH}$ range from 5.0 to 7.5. The $\mathrm{pH}$–rate profile described by specific acid–base catalysis and hydrolysis by water molecules agreed with the experimental results. Arrhenius plots showed the temperature dependence of Gln degradation, and the apparent activation energy at $\mathrm{pH}$ 6.41 was determined to be $\pu{9.87 \times 10^4 J mol−1}$.

Factors affecting the stability of ʟ-glutamine in solution has also been studied (Ref.2). They also found that glutamine degradation resulted in the equimolar formation of ammonia and no associated formation of glutamate. At $\pu{22–24 ^\circ C}$, the degradation rate of glutamine was variable depending on the type of solution used. It was 0.23% in water $\mathrm{pH}$ 6.5; 0.22% in dextrose/water (15% $w/v$); 0.8% in mixed total parenteral nutrition (TPN) solution; and on the $\mathrm{pH}$, molarity and type of buffer used. The degradation rate was essentially unaffected by light and $\ce{O2}$.
Nonetheless, the solubility of ʟ-glutamine in water increases with temperature (Ref.3).
References:

Kanji Arii, Hideyuki Kobayashi, Toshiya Kai, Yukifumi Kokuba, &quot;Degradation kinetics of L-glutamine in aqueous solution,&quot; European Journal of Pharmaceutical Sciences 1999, 9(1), 75-78 (https://doi.org/10.1016/S0928-0987(99)00047-0).
K. Khan, M. Elia, &quot;Factors affecting the stability of ʟ-glutamine in solution,&quot; Clinical Nutrition 1991, 10(4), 186-192 (https://doi.org/10.1016/0261-5614(91)90037-D).
Jan P. Amend, Harold C. Helgeson, “Solubilities of the common ʟ-$\alpha$-amino acids as a function of temperature and solution $\mathrm{pH}$,” Pure and Applied Chemistry 1997, 69(5), 935-942 (https://doi.org/10.1351/pac199769050935).