## 2 Nutritional Value
### Proteins and Amino Acids  
Mushrooms contain relatively high protein contents compared to animal products, but usually rank below animal meats [8]. However, it is reported that pre- and post-harvest conditions affect the nutritional and chemical composition of mushrooms. Moreover, different mushrooms' developmental stages exhibit different amounts of protein and amino acid contents [20; 26; 39; 40]. _A. bisporus_ is rich in different forms of amino acid (Figure 2).  
The amino acids continuously assimilate to produce urea, which contributes to the overall mushroom's total nitrogen contents [41]. Post-harvested mushrooms were reported to shown protease activity [42]. Mushrooms growing on different substrates display variable protein contents as reported by different researchers around the world. [PERSON] and [PERSON] [43] reported that major forms of amino acids in _A. bisporus_ include aspartic acid, serine, glycine, threonine, glutamine, valine, cysteine, alanine, leucine, isoleucine, lysine, histidine, proline, arginine, tyrosine, and noroleucine. Moreover, crude protein contents in _A. bisporus_ ranged from 19-38% on a dry weight basis. Several studies in the past have focused on determining the overall protein and amino acid content of _A. bisporus_. According to [PERSON] et al. [44], 11.01% protein contents were found in _A. bisporus_. [PERSON] et al. [22] recorded the presence of  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Nutritional Group** & **Components** & **Amount** & **Unit** & **References** \\ \hline \multirow{4}{*}{Carbohydrates} & Total sugars & 4.50 & & \\  & Fructose & 2.62 & g 100 g\({}^{-1}\) FW & [30; 32] \\ \cline{2-5}  & Mannitol & 23.62 & & \\ \cline{2-5}  & Trehalose & 1–3 & \% DW & \\ \hline \multirow{4}{*}{Indol compounds} & Indoloacetic acid & 0.19 & & \\  & Tryptamin & 0.06 & & \\  & Kynureic acid & 6.21 & & \\  & Melatonin & 0.11 & & \\  & Serotonin & 5.21 & & \\  & L–Typtophan & 0.39 & & \\ \hline \multirow{4}{*}{Vitamins} & Niacin & 42.0 & & \\  & Vitamin B1 & 0.6 & & \\  & Vitamin B2 & 5.1 & & \\  & Vitamin B3 & 43.0 & & \\  & Vitamin C & 17.0 & & mg 100 g\({}^{-1}\) DW & \\  & \(\gamma\)-Tocopherol & 2–3 & & [28; 33; 34] \\  & \(\alpha\)-Tocopherol & 1–4 & & \\  & \(\delta\)-Tocopherol & 1.0 & & \\ \cline{2-5}  & Folic acid & 450 & & \\  & Vitamin B12 & 0.8 & & \\  & Vitamin D & 3.0 & & \\ \hline \multirow{4}{*}{Phenolic compounds} & Ferulic acid & 42.83 & & \\  & Gallic acid & 280.45 & & \\  & Cinnamic acid & 0.38 & & \\  & Myrietin & 2729.46 & & \\  & Caffe acid & 392.51 & & \\  & Catechins & 56.74 & mg kg\({}^{-1}\) DW & [23; 30; 35; 36] \\  & Procatechic acid & 83.26 & & \\  & \(p\)-Coumaric acid & 2.31 & & \\  & Total phenols & 277–687 & & \\  & Free phenols & 176–487 & & \\ \hline \multirow{4}{*}{Sterols} & Ergosta-7, 22-deiniol & 2.45 & & \\  & Ergosterol & 186.1 & & \\  & Ergosta-7-enol & 1.73 & & \\  & Ergosta-5,7-deiniol & 6.05 & & \\ \hline \hline \end{tabular} Note: mg = Milligram; kg = Kilogram; g = Gram; DW = Dry weight; FW = Fresh weight.  
\end{table}
Table 2: _Cont._proteins up to 11.01% in _A. bisporus_. However, [PERSON] et al. [45] found that _A. bisporus_ contained 17.7-24.7% protein contents while [PERSON] et al. [25] reported the presence of 29.1% protein contents in _A. bisporus_. These results indicate that the protein contents vary in _A. bisporus_ based on the usage of different growth substrates.  
Recently, a novel class of specific ribonucleases, known as \"ribotoxin-like proteins,\" have been discovered [46; 47]. It has been found that ribotoxins are widely distributed among various species of mushrooms. [PERSON] et al. [46] isolated a ribotoxin, i.e., \"Ageritin,\" from _Agrocybe aegerita_ and found that it possessed multiple biological activities, i.e., antibacterial, antiviral, endonuclease, nuclease, and cytotoxic activities, which could be employed in plants through transgenic techniques to enhance resistance against viruses, bacteria, and fungi.