EC 3.4.23.42     
Accepted name: thermopsin
Reaction: Similar in specificity to pepsin A preferring bulky hydrophobic amino acids in P1 and P1′
Comments: From the thermophilic archaeon Sulfolobus acidocaldarius. Maximally active at pH 2 and 90 °C. Weakly inhibited by pepstatin but shows no sequence similarity to pepsin. Type example of peptidase family A5.
References:
1.  Lin, X. and Tang, J. Thermopsin. Methods Enzymol. 248 (1995) 156–168. [PMID: 7674919]
[EC 3.4.23.42 created 1992 as EC 3.4.99.43, transferred 2000 to EC 3.4.23.42]