凝乳酶
凝乳酶（英語：Chymosin或Rennin）是一種在皺胃酶中發現的蛋白酶。它是屬於MEROPS A1家族的天冬氨酸蛋白酶。它是由新生反芻動物在皺胃內壁產生的，用於凝結它們攝入的乳汁，從而在腸道中停留更長時間並更好地吸收。它廣泛用於奶酪的生產。如今，牛凝乳酶在大腸桿菌、黑麴黴和Kluyveromyces lactis中重組生產，作為替代來源。
| 凝乳酶 | |||||||
|---|---|---|---|---|---|---|---|
| |||||||
| 牛凝乳酶與抑制劑CP-113972複合物的晶體結構。[1] | |||||||
| |||||||
| 識別碼 | |||||||
| EC編號 | 3.4.23.4 | ||||||
| CAS號 | 9001-98-3 | ||||||
| 數據庫 | |||||||
| IntEnz | IntEnz瀏覽 | ||||||
| BRENDA | BRENDA入口 | ||||||
| ExPASy | NiceZyme瀏覽 | ||||||
| KEGG | KEGG入口 | ||||||
| MetaCyc | 代謝路徑 | ||||||
| PRIAM | 概述 | ||||||
| PDB | RCSB PDB PDBj PDBe PDBsum | ||||||
| 基因本體 | AmiGO / EGO | ||||||
| |||||||
發生
雖然凝乳酶著名於由反芻動物在皺胃內壁產生，但它其實廣泛存在於所有四足類動物中。[2]凝乳酶由新生哺乳動物的胃主細胞產生，[3]用於凝固它們攝入的乳汁，從而在腸道中停留更長時間並更好地吸收。產生凝乳酶的非反芻動物包括豬、貓、海豹[4]和雞。[2]
一項研究報告稱在一些人類嬰兒身上發現了一種類似凝乳酶的酶，[5]但其他研究未能複製這一發現。[6]人類在1號染色體上有一個不產生蛋白質的凝乳酶假基因。[4][7]人類還有其他蛋白質可以消化牛奶，例如胃蛋白酶和脂肪酶。[8]:262
除了人類等靈長類動物外，其他一些哺乳動物也失去了凝乳酶基因。[2]
參考文獻
- ^ PDB 1CZI; Groves MR, Dhanaraj V, Badasso M, Nugent P, Pitts JE, Hoover DJ, Blundell TL. A 2.3 A resolution structure of chymosin complexed with a reduced bond inhibitor shows that the active site beta-hairpin flap is rearranged when compared with the native crystal structure (PDF). Protein Engineering. October 1998, 11 (10): 833–40. PMID 9862200. doi:10.1093/protein/11.10.833
.
- ^ 2.0 2.1 2.2 Lopes-Marques M, Ruivo R, Fonseca E, Teixeira A, Castro LF. Unusual loss of chymosin in mammalian lineages parallels neo-natal immune transfer strategies. Molecular Phylogenetics and Evolution. November 2017, 116: 78–86. PMID 28851538. doi:10.1016/j.ympev.2017.08.014.
- ^ Kitamura N, Tanimoto A, Hondo E, Andrén A, Cottrell DF, Sasaki M, Yamada J. Immunohistochemical study of the ontogeny of prochymosin--and pepsinogen-producing cells in the abomasum of sheep. Anatomia, Histologia, Embryologia. August 2001, 30 (4): 231–5. PMID 11534329. S2CID 7552821. doi:10.1046/j.1439-0264.2001.00326.x.
- ^ 4.0 4.1 Staff, Online Mendelian Inheritance in Man (OMIM) Database. Last updated February 21, 1997 Chymosin pseudogene; CYMP prochymosin, included, in the OMIM （頁面存檔備份，存於互聯網檔案館）
- ^ Henschel MJ, Newport MJ, Parmar V. Gastric proteases in the human infant. Biology of the Neonate. 1987, 52 (5): 268–72. PMID 3118972. doi:10.1159/000242719.
- ^ Szecsi PB, Harboe M. Chapter 5: Chymosin. Rawlings ND, Salvesen G (編). Handbook of Proteolytic Enzymes 1. 2013: 37–42. doi:10.1016/B978-0-12-382219-2.00005-3 （英語）.
- ^ Fox PF. Cheese: Chemistry, Physics and Microbiology. 28 February 1999. ISBN 9780834213388.
- ^ Sanderson IR, Walker WA. Development of the gastrointestinal tract. Hamilton, Ontario: B.C. Decker. 1999. ISBN 978-1-55009-081-9.
延申閱讀
- Foltmann B. A review on prorennin and rennin. Comptes-Rendus des Travaux du Laboratoire Carlsberg. 1966, 35 (8): 143–231. PMID 5330666.
- Visser S, Slangen CJ, van Rooijen PJ. Peptide substrates for chymosin (rennin). Interaction sites in kappa-casein-related sequences located outside the (103-108)-hexapeptide region that fits into the enzyme's active-site cleft. The Biochemical Journal. June 1987, 244 (3): 553–8. PMC 1148031 . PMID 3128264. doi:10.1042/bj2440553.