Table 2.
Protease family, accession number, source organism, degrading substrate, and some physical characteristics of sequenced keratinolytic enzymes.
| NCBI accession number | Source organism | Original sources | Substrate | No. of AA | Mw (kDa) | Optimum conditions (pH, temp.) | Reference |
|---|---|---|---|---|---|---|---|
| S1 family | |||||||
| BAM67011 | Paenarthrobacter nicotinovorans | Bivalve | Keratin azure | 330 | 23 | – | (Sone et al., 2015) |
| AAO06113 | Nocardiopsis sp. TOA-1 | Tile joint | Keratin | 384 | – | 12.5, 60 °C | (Mitsuiki et al., 2004) |
| AQX39246 | Streptomyces albidoflavus | Poultry soil | Feather | 360 | 36 | 10.0, 50 °C | (Ma et al., 2017) |
| CAH05008 | Streptomyces fradiae | – | Keratin azure | 307 | 26 | 9.0, 55 °C | (Li et al., 2007) |
| S8 family | |||||||
| 1205229A | Parengyodontium album | Soil | Keratin | 277 | 28.9 | 7.5, 37 °C | (Ebeling et al., 1974; Jany et al., 1986) |
| AGK12420 | Stenotrophomonas maltophilia | Poultry farm | Feather | 634 | 48 | 8.0, 60 °C | (Fang et al., 2014) |
| AGK29593 | Stenotrophomonas maltophilia | Poultry farm | Feather | 580 | 40 | 8.0, 60 °C | (Fang et al., 2014) |
| AAK61552 | Fervidobacterium pennivorans | Hot spring | Feather | 699 | 130 | 10.0, 80 °C | (Friedrich and Antranikian, 1996; Kim et al., 2004) |
| ADD51544 | Thermoactinomyces sp. CDF | Campus soil | Feather | 384 | 30 | 11.0, 80 °C | (Wang et al., 2015) |
| AAS86761 | Bacillus licheniformis | – | Feather | 379 | – | – | (Ramnani and Gupta, 2004) |
| AIY62812 | Bacillus subtilis | Poultry soil | Feather | 362 | – | – | (Gupta and Singh, 2013) |
| AKR05134 | Bacillus amyloliquefaciens | – | Feather | 382 | 27 | 11.0, 50 °C | (Yang et al., 2016) |
| ANQ68333 | Bacillus pumilus | Compost | Feather | 383 | 38 | – | (Fellahi et al., 2016) |
| ANQ68334 | Bacillus pumilus | Compost | Feather | 383 | 38 | – | (Fellahi et al., 2016) |
| ACC94305 | Bacillus cereus | Soil | Feather | 917 | 80 | 8.5, 50 °C | (Ghosh et al., 2009) |
| ADD64465 | Bacillus halodurans JB99 | Sugarcane molasses | Feather | 361 | 29 | 11.0, 70 °C | (Shrinivas and Naik, 2011) |
| ARH33809 | Meiothermus taiwanensis | Hot spring | Feather | 400 | 41.3 | 10.0, 65 °C | (Wu et al., 2017) |
| BAQ36632 | Stenotrophomonas maltophilia | – | Keratin azure | 589 | 42 | 10.5, 50 °C | (Jankiewicz et al., 2016) |
| APY18977 | Thermoactinomyces sp. YT06 | Poultry compost | Feather | 389 | 35 | 9.0, 65 °C | (Wang et al., 2017) |
| AAS45672 | Trichophyton benhamiae | Humans | Keratin azure | 399 | 39.7 | – | (Jousson et al., 2004) |
| AAS45666 | Trichophyton benhamiae | Humans | Keratin azure | 400 | 28.2 | – | (Jousson et al., 2004) |
| AAR02423 | Trichophyton rubrum | Humans | Keratin azure | 399 | 28.9 | – | (Jousson et al., 2004) |
| AAR11461 | Trichophyton rubrum | Humans | Keratin azure | 424 | 32.6 | – | (Jousson et al., 2004) |
| AAR02424 | Trichophyton rubrum | Humans | Keratin azure | 396 | 29.0 | – | (Jousson et al., 2004) |
| AJD23187 | Onygena corvina | Horn | Pig bristle | 393 | – | – | (Huang et al., 2015) |
| AJD23193 | Onygena corvina | Horn | Pig bristle | 369 | – | – | (Huang et al., 2015) |
| CAD24008 | Microsporum canis | – | Cat keratin | 485 | 51.3 | – | (Descamps et al., 2002) |
| CAD24009 | Microsporum canis | – | Cat keratin | 427 | 46.1 | – | (Descamps et al., 2002) |
| CAD24010 | Microsporum canis | – | Keratin azure | 397 | 31.5 | – | (Descamps et al., 2002) |
| AAA32703 | Aspergillus niger | – | Keratin azure | 416 | 43.8 | 8.0, 70 °C | (Chen et al., 2015; (Jarai et al., 1994) |
| AHY02992 | Trichophyton mentagrophytes | – | Keratin azure | 412 | – | – | (Yohko et al., 2014) |
| S9 family | |||||||
| AAN03632 | Trichophyton rubrum | Clinical isolate | Keratin | 726 | 78 | 7.0–9.0, − | (Monod et al., 2005) |
| AAS76665 | Trichophyton rubrum | Clinical isolate | Keratin | 775 | 84 | 7.0–9.0, − | (Monod et al., 2005) |
| S10 family | |||||||
| AAS76667 | Trichophyton rubrum | Clinical isolate | Keratin | 652 | 90 | – | (Zaugg et al., 2008) |
| AAS76666 | Trichophyton rubrum | Clinical isolate | Keratin | 662 | 85 | – | (Zaugg et al., 2008) |
| S16 family | |||||||
| AMW33508 | Fervidobacterium islandicum | Hot spring | Feather | 631 | 88 | – | (Kang et al., 2020) |
| M3 family | |||||||
| AJD23200 | Onygena corvina | Horn | Pig bristle | 783 | – | – | (Huang et al., 2015) |
| M4 family | |||||||
| ADP00718 | Pseudomonas aeruginosa | Garden soil | Feather | 475 | – | – | (Sharma and Gupta, 2010) |
| AJD77429 | Geobacillus stearothermophilus | – | Keratin azure | 546 | 57 | 9.0, 60 °C | (Gegeckas et al., 2015) |
| M14 family | |||||||
| ABG67896 | Trichophyton rubrum | Clinical isolate | Keratin | 422 | 42 | – | (Zaugg et al., 2009, Zaugg et al., 2008) |
| M16 family | |||||||
| AMW32060 | Fervidobacterium islandicum | Hot spring | Feather | 406 | 44 | – | (Kang et al., 2020) |
| M28 family | |||||||
| AAS76670 | Trichophyton rubrum | Clinical isolate | Keratin | 373 | 58 | 7.0, 50 °C | (Monod et al., 2005) |
| AJD23165 | Onygena corvina | Horn | Pig bristle | 374 | – | – | (Huang et al., 2015) |
| CAH03796 | Streptomyces fradiae | – | Feather | 461 | 36 | 8.0, 60 °C | (Wu et al., 2010) |
| AJD23207 | Onygena corvina | Horn | Pig bristle | 493 | – | – | (Huang et al., 2015) |
| AAS76669 | Trichophyton rubrum | Clinical isolate | Keratin | 495 | 33 | 7.0, 50 °C | (Monod et al., 2005) |
| M32 family | |||||||
| AMW32563 | Fervidobacterium islandicum | Hot spring | Feather | 489 | 107 | 7.0, 80 °C | (Lee et al., 2015a) |
| M36 family | |||||||
| BAM84176 | Fusarium oxysporum | Soil | Wool cuticle | 632 | 46.8 | 7.0, 50 °C | (Chaya et al., 2014) |
| CAD35288 | Microsporum canis | – | Keratin azure | 633 | – | – | (Brouta et al., 2002) |
| AJD23141 | Onygena corvina | Horn | Pig bristle | 634 | – | – | (Huang et al., 2015) |
| M38 family | |||||||
| AMW33776 | Fervidobacterium islandicum | Hot spring | Feather | 345 | 42 | – | (Kang et al., 2020) |
| M55 family | |||||||
| AMW33601 | Fervidobacterium islandicum | Hot spring | Feather | 279 | 31 | – | (Kang et al., 2020) |