酪蛋白
酪蛋白（Casein，源自拉丁语的caseus，意思為乾酪。中文或稱乾酪素），含有磷酸根，屬於磷蛋白(αS1, αS2, β, κ)。酪蛋白是哺乳類的奶的主要成份，在牛奶含有的蛋白質中佔80%，人奶含有的蛋白質中則佔 20% - 45%。[1]
組成
酪蛋白含有大量的脯氨酸，這些脯氨酸通常不參與有機體中的化學反應。酪蛋白也不具雙硫鍵，因此它沒有明顯的三級結構。酪蛋白呈略疏水性，在牛奶中被包覆在稱為酪蛋白膠束的囊中。它與介面活性劑型的膠束並不相同，因為它們的疏水端在外，而且它們是圓形的；更大的不同點是，其膠束內部是高度親水的。膠束內的酪蛋白受鈣離子與疏水效應而被束縛。目前有許多不同的模型試圖解釋膠束內酪蛋白的特殊結構。[2] 其中一種模型認為膠束是由許多更小的膠束組成，而κ-酪蛋白包在更小的膠束周圍。[3][4] 另一個模型推測膠束是由酪蛋白之間交錯的極細纖維組成。[5]最新提出的模型[6]則認為酪蛋白間的雙鍵膠合而構成了膠束。這些模型的相似處在於他們都認為膠束是酪蛋白聚集產生的微小懸浮粒子，並被可溶於水的κ-酪蛋白所包覆。
酪蛋白的等電點是4.6，而牛奶的pH值是6.6，因此可知酪蛋白在牛奶中帶負電。純化的酪蛋白在水中或中性鹽類溶液中均不溶，但在稀的鹼性溶液中可溶，並且也溶於草酸鈉、醋酸鈉之溶液。
應用
酪蛋白之應用廣泛，除了是起司的主要材料之外，也可用作營養補給品、食品原料、油漆、木膠、塑膠纖維或牙醫材料[8]。
參考文獻
- ^ Kunz, C; Lonnerdal, B. Human-milk proteins: analysis of casein and casein subunits.... American Journal of Clinical Nutrition (The American Society for Clinical Nutrition). 1990, 51 (1): 37–46 [14 January 2011]. PMID 1688683. （原始内容存档于2011-05-27）.
- ^ Dalgleish DG. Casein micelles as colloids. Surface structures and stabilities. Journal of Dairy Science. 1 November 1998, 81 (11): 3013–8 [2013-10-17]. doi:10.3168/jds.S0022-0302(98)75865-5. （原始内容存档于2019-09-05）.
- ^ Walstra, Pieter. The voluminosity of bovine casein micelles and some of its implications. Journal of Dairy Research. 1979, 46: 317–323. ISSN 1469-7629. doi:10.1017/S0022029900017234.
- ^ Lucey JA. Formation and Physical Properties of Milk Protein Gels. Journal of Dairy Science. 1 February 2002, 85 (2): 281–94 [2013-10-17]. PMID 11913691. doi:10.3168/jds.S0022-0302(02)74078-2. （原始内容存档于2020-01-31）.
- ^ Holt C. Structure and stability of bovine casein micelles. Adv Protein Chem. 1992, 43: 63–151. PMID 1442324. doi:10.1016/S0065-3233(08)60554-9.
- ^ Horne DS. Casein interactions: Casting light on the black boxes, the structure in dairy products. Int Dairy J. March 1998, 8 (3): 171–7. doi:10.1016/S0958-6946(98)00040-5.
- ^ CCMR - Ask A Scientist!. Ccmr.cornell.edu. 1998-09-24 [2011-09-29]. （原始内容存档于2011-09-28）.
- ^ "Industrial Casein" 互联网档案馆的存檔，存档日期2012-11-12., National Casein Company
延伸閱讀
- Campbell, T. Colin and Campbell, Thomas M. The China Study. Benbella Books, 2006.
- Green VA, Pituch KA, Itchon J, Choi A, O'Reilly M, Sigafoos J. Internet survey of treatments used by parents of children with autism. Res Dev Disabil. 2006, 27 (1): 70–84. PMID 15919178. doi:10.1016/j.ridd.2004.12.002.
- Lucarelli S, Frediani T, Zingoni AM, et al. Food allergy and infantile autism. Panminerva Med. September 1995, 37 (3): 137–41. PMID 8869369.
- Rao MB, Tanksale AM, Ghatge MS, Deshpande VV. Molecular and biotechnological aspects of microbial proteases. Microbiol Mol Biol Rev. 1 September 1998, 62 (3): 597–635 [2018-02-02]. PMC 98927
. PMID 9729602. （原始内容存档于2019-06-14）. - Engel RW, Copeland DH. The influence of dietary casein level on tumor induction with 2-acetylaminofluorene. Cancer Res. 1 December 1952, 12 (12): 905–8 [2018-02-02]. PMID 13009679. （原始内容存档于2013-01-12）.
- Manninen, A.H. Protein metabolism in exercising humans with special reference to protein supplementation. Master thesis (PDF). Department of Physiology, Faculty of Medicine, University of Kuopio, Finland. 2002 [2018-02-02]. （原始内容 (PDF)存档于2013-12-28）.
- Robert H. Demling; Leslie DeSanti. Effect of a Hypocaloric Diet, Increased Protein Intake and Resistance Training on Lean Mass Gains and Fat Mass Loss in Overweight Police Officers. Annals of Nutrition & Metabolism. 2000, 44 (1): 21–29. doi:10.1159/000012817.
外部連結
- Healing Thresholds – summarizes scientific evidence on casein-free diets and other therapies for autism
- Eating without Casein （页面存档备份，存于互联网档案馆） a practical guide to eating and living without casein
- 醫學主題詞表（MeSH）：Caseins
- 時代雜誌 magazine, Monday, December 6, 1936 Lanital （页面存档备份，存于互联网档案馆）
- Time magazine, Monday, August 29, 1938 Wool from Cows （页面存档备份，存于互联网档案馆）
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