Serum albumin, often referred to simply as albumin, is the most abundant plasma protein in humans and other mammals. Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues. It also acts as a plasma carrier by non-specifically binding several hydrophobic steroid hormones and as a transport protein for hemin and fatty acids.
Types
The human version is human serum albumin.
Bovine serum albumin, or BSA, is commonly used in immunodiagnostic procedures, clinical chemistry reagents, cell culture media, protein chemistry research and molecular biology laboratories (usually to leverage its non-specific protein binding properties).
[edit] General characteristics
Albumin (when ionized in water at pH 7.4, as found in the body) is negatively charged. The glomerular basement membrane is also negatively charged in the bodysome studies suggest that this prevents the filtration of albumin in the urine. According to this theory, that charge plays a major role in the selective exclusion of albumin from the glomerular filtrate. A defect in this property results in nephrotic syndrome leading to albumin loss in the urine. Nephrotic syndrome patients are sometimes given albumin to replace the lost albumin.
Because smaller animals (for example rats) function at a lower blood pressure, they need less oncotic pressure to balance this, and thus need less albumin to maintain proper fluid distribution.
Serum albumin contains eleven distinct binding domains for hydrophobic compounds. One hemin and six long-chain fatty acids can bind to serum albumin at the same time
Human serum albumin is the most abundant protein in human blood plasma. It is produced in the liver. Albumin comprises about half of the blood serum protein. It is soluble and monomeric.
The gene for albumin is located on chromosome 4 and mutations in this gene can result in various anomalous proteins. The human albumin gene is 16,961 nucleotides long from the putative 'cap' site to the first poly(A) addition site. It is split into 15 exons which are symmetrically placed within the 3 domains that are thought to have arisen by triplication of a single primordial domain.
Albumin is synthesized in the liver as preproalbumin which has an N-terminal peptide that is removed before the nascent protein is released from the rough endoplasmic reticulum. The product, proalbumin, is in turn cleaved in the Golgi vesicles to produce the secreted albumin.
The reference range for albumin concentrations in blood is 30 to 50 g/L. It has a serum half-life of approximately 20 days. It has a molecular mass of 67 kDa.
Functions of albumin
Maintains oncotic pressure
Transports thyroid hormones
Transports other hormones, particularly fat soluble ones
Transports fatty acids ("free" fatty acids) to the liver
Transports unconjugated bilirubin
Transports many drugs, and serum albumin levels can affect the half-life of drugs.
Competitively binds calcium ions (Ca2+)
Buffers pH
[edit] Pathology
[edit] Hypoalbuminemia
Low blood albumin levels (hypoalbuminemia) can be caused by:
liver disease / Cirrhosis of the liver (most commonly)
Decreased production (as in starvation/malnutrition/malabsorption)
Excess excretion by the kidneys (as in nephrotic syndrome)
Excess loss in bowel (protein losing enteropathy e.g. Menetrier's)
Burns (Plasma loss in the absence of skin barrier)
Redistribution (hemodilution [as in Pregnancy], increased vascular permeability or decreased lymphatic clearance)
Acute disease states (referred to as a negative acute phase protein)
Mutation causing analbuminemia (very rare)
[edit] Hyperalbuminemia
Typically is a sign of severe dehydration.
[edit] Glycation (Glycosylation) of Serum Albumin
It has been known for a long time that human blood proteins like hemoglobin [1] and serum albumin [2][3] may undergo a slow non-enzymatic glycation, mainly by formation of a Schiff base between ε-amino groups of lysine (and sometimes arginine) residues and glucose molecules in blood (Maillard reaction). This reaction can be inhibited in the presence of antioxidant agents [4]. Although this reaction may happen normally [5] , elevated glycoalbumin is observed in diabetes mellitus [6].
Glycation has the potential to alter the biological structure and function of the serum albumin protein [7][8][9][10]. Moreover, the glycation finally can result in the formation of Advanced Glycosylation End Products (AGE), which result in abnormal biological effects. Accumulation of AGEs leads to tissue damage via alteration of the structures and functions of tissue proteins, stimulation of cellular responses, through receptors specific for AGE-proteins, and via generation of reactive oxygen intermediates. AGEs also react with DNA, thus causing mutations and DNA transposition. Thermal processing of proteins and carbohydrates brings major changes in allergenicity. AGEs are antigenic and represent many of the important neoantigens found in cooked or stored foods [11]. They also interfere with the normal product of nitric oxide in cells [12].
Although there are several lysine and arginine residues in the serum albumin structure, very few of them can take part in the glycation reaction [13][14]. It is not clear exactly why only these residues are glycated in serum albumin [15].
[edit] Testing for albumin loss via the kidneys
In the healthy kidney, albumin's size and negative electric charge exclude it from excretion in the glomerulus. This is not always the case, as in some diseases including diabetic nephropathy, a major complication of uncontrolled diabetes where proteins can cross the glomerulus. The lost albumin can be detected by a simple urine test.[16] Depending on the amount of albumin lost, a patient may have normal renal function, microalbuminuria, or albuminuria.
[edit] Amino Acid Sequence
The approximate sequence of human serum albumin is:
MKWVTFISLL FLFSSAYSRG VFRRDAHKSE VAHRFKDLGE ENFKALVLIA FAQYLQQCPF EDHVKLVNEV TEFAKTCVAD ESAENCDKSL HTLFGDKLCT VATLRETYGE MADCCAKQEP ERNECFLQHK DDNPNLPRLV RPEVDVMCTA FHDNEETFLK KYLYEIARRH PYFYAPELLF FAKRYKAAFT ECCQAADKAA CLLPKLDELR DEGKASSAKQ RLKCASLQKF GERAFKAWAV ARLSQRFPKA EFAEVSKLVT DLTKVHTECC HGDLLECADD RADLAKYICE NQDSISSKLK ECCEKPLLEK SHCIAEVEND EMPADLPSLA ADFVESKDVC KNYAEAKDVF LGMFLYEYAR RHPDYSVVLL LRLAKTYETT LEKCCAAADP HECYAKVFDE FKPLVEEPQN LIKQNCELFE QLGEYKFQNA LLVRYTKKVP QVSTPTLVEV SRNLGKVGSK CCKHPEAKRM PCAEDYLSVV LNQLCVLHEK TPVSDRVTKC CTESLVNRRP CFSALEVDET YVPKEFNAET FTFHADICTL SEKERQIKKQ TALVELVKHK PKATKEQLKA VMDDFAAFVE KCCKADDKET CFAEEGKKLV AASQAALGL
Where the italicized first 24 amino acids are signal and propeptide portions not observed in the transcribed, translated and transported protein but present in the gene. There are 609 amino acids in this sequence with only 585 amino acids in the final product observed in the blood.
目录1 拼音2 英文参考3 概述4 血清球蛋白的医学检查 4.1 检查名称4.2 分类4.3 取材4.4 血清球蛋白的测定原理4.5 试剂4.6 操作方法4.7 正常值4.8 化验结果临床意义4.9 附注4.10 相关疾病 1 拼音xuè qīng qiú dàn bái
2 英文参考globoglycoid
seroglobulin
serum casein
serum globulin
serum globulins
serum globulins,gamma
serumglobulin
SG
3 概述血清球蛋白是多种蛋白质的混合物，包括含量较多具有防御作用的免疫球蛋白和补体、多种糖蛋白、金属结合蛋白、多种脂蛋白、酶类等。球蛋白的含量一般由总蛋白减白蛋白得到。
4 血清球蛋白的医学检查4.1 检查名称血清球蛋白
4.2 分类血液生化检查 >蛋白质测定
4.3 取材血液
4.4 血清球蛋白的测定原理溴甲酚绿（BCG）在pH4.2的环境中，在有非离子去垢剂Brij35存在时，可与白蛋白形成蓝绿色复合物，在波长630nm处有最大吸收光，并与白蛋白浓度成正比，与同样处理的白蛋白标准比较，可求得血清中球蛋白含量。
4.5 试剂（1）0.5mol/L琥珀酸缓冲液（pH4.0±0.05）：称取琥珀酸56g于800ml蒸馏水中用1mol/L氢氧化钠调到pH4.1±0.05，加水稀释至1000ml，此液置4℃冰箱保存。
（2）BCG贮存液（10mmol/L）：取BCG1.80g溶解于1mol/L氢氧化钠5ml中，
用蒸馏水稀释至250ml。
（3）叠氮钠贮存液：溶解叠氮钠40g于1000ml蒸馏水中。
（4）聚氧化乙化乙烯月桂醚（Brij35）贮存液：称取聚氧化乙化乙烯月桂醚25g于约80ml蒸馏水中，加温助溶，然后加蒸馏水至100ml。
（5）BCG试剂：于1升容量瓶中盛蒸馏水约400ml，加琥珀酸缓冲液100ml，用吸管准确加入BCG贮存液8.0ml，用蒸馏水将吸管壁上残留的BCG冲洗干净，加叠氮钠2.5ml，聚氧化乙化乙烯月桂醚2.5ml，最后用蒸馏水稀释至刻度，配好的BCG试剂pH应为4.15±0.05。
（6）40g/L白蛋白标准应用液：可用定值参考血清作白蛋白标准应用液。均需置冰箱保存。
4.6 操作方法见表1。
混匀，室温放置10min，在波长630nm，用空白管调零点，读取各管的吸光度。
标本混浊，可做标本空白管（血清0.02ml加琥珀酸缓冲液4ml），再用测定管吸光度减去标本空白管吸光度后，计算结果由总蛋白－白蛋白＝球蛋白含量。
4.7 正常值乙醛酸比色法：20～30g/L （2.0～3.0g/dl）。
4.8 化验结果临床意义（1）升高：
①感染引起机体免疫反应增强：慢性病毒性肝炎、活动性结核病、黑热病、血吸虫病、疟疾、亚急性细菌性心内膜炎等。
②自身免疫性疾病时的机体免疫功能亢进：系统性红斑狼疮（SLE）、硬皮病、风湿热、类风湿性关节炎、肝硬化等。
③骨髓瘤、淋巴瘤、白血病、部分恶性肿瘤等。
④肾病综合征、过敏反应、肺炎、丝虫病。
⑤生理性：血清水分减少、血液浓缩。
（2）降低：
①合成减少：库欣综合征、使用肾上腺皮质激素或其他免疫抑制剂。
②γ球蛋白缺乏症。
③放射治疗后或氮芥中毒。
④正常婴儿出生后至3岁。
4.9 附注（1）小儿出生后至3岁，血清球蛋白测定降低，属生理性减少。
（2）长期应用免疫抑制剂或肾上腺皮质激素治疗，可使球蛋白合成减少。
4.10 相关疾病卡介苗（BCG Vaccine）是由减毒牛型结核杆菌悬浮液制成的活菌苗，具有增强巨噬细胞活性，加强巨噬细胞杀灭肿瘤细胞的能力，活化T淋巴细胞，增强机体细胞免疫的功能。
最早由法国科学家卡尔梅特（Calmette)和介朗（Guérin)研制成功。
取本品2瓶（120mg），溶于40～50ml生理盐水并充分摇匀，按外科导尿手术，将导尿管插入膀胱腔，将稀释好的药液，经导尿管注入。注入后，患者不断变换体位，如左侧、右侧、仰卧和俯卧，各约30分钟，经2小时后自行排除药液。对高龄患者或体弱者卡介苗用量可减半（60mg/次）。
卡介苗灌注一般在手术后1～2周待受损组织恢复后进行。给药周期为：开始每周灌注1次，共6次；继之每2周1次，共3次；以后每月1次，直至1年，总计19次。每半年1次检查膀胱癌有无复发。必要时每月1次再持续1～2年以巩固疗效。
以上内容参考：百度百科-卡介苗
欢迎分享，转载请注明来源：优选云
微信扫一扫
支付宝扫一扫
