Thermostability is one of the significant characteristics among industrial enzymes because of higher reactions rate in higher temperature. For this reason, a continuous effort exists on discovering new qualified enzymes or improving current enzymes by protein engineering techniques. In the last way, some factors are more interested to change than others including: surface loops, disulfide bonds, metal binding, CG-rich codons, ratio of charged amino acids to uncharged, amino acid preferences, Proline frequency, thermolabile residues, α/β content of protein, no. of hydrogen bonds, ionic interactions, hydrophobic interactions, compact packing, and stability of α-helices. In the current study, previously mentioned factors were investigated among 35 thermophile and mesophile α-amylases from different sources to find most effective factors that have a significant difference between two isoforms. In other hand, because amylases are one of representative for industrial enzymes therefore this makes it possible to generalizing the current work outcomes to other industrial enzymes. The following results concluded from the study: di-sulfide bonds have a minimum impact on the thermal stability and presences of thermolabile amino acids have a maximum. The other factors sorted between upper and lower impact levels but meanwhile some other factors dose not participates in increase or decreasing the thermostability.

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