Apolipoproteins arePlasma LipoproteinInproteinSome can combine and transport blood lipids to various tissues of the bodymetabolizeAnd utilized proteins.A large number of studies have found that apolipoprotein gene mutations, forming differentAlleletypePolymorphismAnd further form apolipoproteins with different phenotypes, which can affect the metabolism and utilization of blood lipids, thus affectingHyperlipidemia、atherosclerosis、Cardiovascular and cerebrovascular diseasesThe occurrence and development of.[1]
Chinese name
Apolipoprotein
Latin name
Apolipoprotein
Specific
The protein portion of plasma lipoproteins
Synthetic site
Mainly in the liver (partially in the small intestine)
loadLipoproteinIt is the protein component of plasma lipoproteins, mainly divided into five categories: A, B, C, D and E.basic function Is carryinglipidStructure of substances and stable lipoproteins, some apolipoproteins and activated lipoproteinsMetabolic enzyme, receptor recognition and other functions.It is mainly synthesized in the liver (partially in the small intestine), named according to the ABC system, and can be divided into several subclassesRoman numeralsexpress.
Apolipoprotein
Apolipoproteins are important components of plasma lipoproteinslipidIn soluble form, it plays an important role in plasma lipoprotein metabolism: (1) promoting lipid transport;(2) Adjustmentenzymatic activity；(3) Guiding plasma lipoproteinCell surface receptorcombination.It is a group of extremely active functionsPlasma protein。
Reference: Apolipoprotein B
Human apolipoproteins are expressed in two forms: apoB-48 and apob-100.The sequence of this gene is in the liver and intestineHistiocyteIs the same, but the product is different.stayHepatocyte4536 productsAmino acid residuePeptide: apoB-100;However, in intestinal cells, the product is apoB-48, which only contains 2152 amino acid residues and lacks apoB-100C-endwithLDL receptorCombinedDomain。The reason is thatmRNAHorizontally, 2153 bitglutamineOfCodonC in CAA is edited as U, forming aTermination codon- UAA, which results in early termination of protein synthesis and synthesis of a newrelative molecular massAbout 250kDa protein.
The analysis coefficient of variation of immunoelectrophoresis diffusion method is 5%
[Biological variation]
1. For liftingantiepilepticIncrease by about 20%ethanolIt increased by about 20%, and hyperlipidemia increased by about 15%.In womenOral contraceptivesIt increased by about 10%, menopause by about 4%, and estrogen by about 3%.
0.5g/L: lower than this value indicates the existence of lipid metabolism disorder and the observation for diet treatment.
Family A classification
Apolipoprotein A family Apolipoprotein A (ApoA) can be divided into ApoA Ⅰ, ApoA Ⅱ and ApoA Ⅳ.ApoA Ⅰ and ApoA Ⅱ are mostly distributed inHDLIt is the main apolipoprotein of HDL.
1、 ApoA Ⅰ
ApoA Ⅰ is the largest component of ApoA family and the main apolipoprotein in HDL.Shore is equal to the first person from HDL in 1968Separation and purificationApoA Ⅰ was obtained.In the mid-1970s, Brewer clarified theamino acidAnd predicted itsSecondary structureKey points of.staymolecular biologyIn the 1980s, Karathanasis and others successively reported human ApoA ⅠcDNAandChromosome DNASequence.Human mature ApoA Ⅰ consists of 243Amino acid residueComposition is singlePolypeptide chain, molecular weight is 28300D.People andRatApoA Ⅰ from monkeys, rabbits, cattle, ducks, mice and other animals has been isolated and purified.ApoA Ⅰ of human and other speciesAmino terminalIs Asp,Carboxyl terminalIt is Gln, and its molecule does not containCysteineandisoleucine。throughIsofocal electrophoresisIt is confirmed that ApoA Ⅰ of human and animal is heterogeneous, with 10 different sub components, at least sixPolymorphism。throughIsoelectric focusingAnd the systematic naming in two-phase electrophoresis, ApoA Ⅰ polypeptide is called Apoa Ⅰ 0, ApoA Ⅰ - 1, ApoA Ⅰ - 2, ApoA Ⅰ+1, ApoA Ⅰ+2, in which ApoA Ⅰ 0 is the most abundant.
2、 ApoA Ⅱ
ApoA Ⅱ is the second high content apolipoprotein in HDL, accounting for 15% of apolipoprotein in HDL2 and 25% of apolipoprotein in HDL3.7%~10% of total apolipoproteins in CM and a small amount in VLDL.Until 1985, the amino acid sequence, cDNA sequence and gene sequence of ApoA Ⅱ proteinAll haveClarification.ApoA Ⅱ is composed of 77 polypeptide chainsAmino acid residueform.ApoA Ⅱ is not addedreducing agentOfSDS-PAGEThe molecular weight is 17000D measured inDimerForm exists.The monomer molecular weight of ApoA Ⅱ is 8700D.The C-terminal amino acid residue of human ApoA Ⅱ protein isglutamate, N end isPyrrolidineKeto acid, lackinghistidine，ArginineandTryptophan。ApoA Ⅱ has polymorphism, the main polymorphismIsoelectric point4.9, while the isoelectric points of polymorphic type with less content are 5.17, 4.68, 4.42 and 4.20.
ApoA Ⅱphysiological functionYes: ① Maintain HDL structure, ApoA Ⅱ peptide 12-31 and peptide 50-77 havephospholipidThe combination ability ofstructural analysisIt is believed that,ResidueDuality formed by 17-30 and 51-62Helical structurePeople ApoA Ⅱ andlipidMolecular basis of binding; ②activationHepatic lipase, used to hydrolyzeTGAnd PL.It is also reported that ApoA Ⅱ can inhibitLCATActivity.ApoA Ⅱ is synthesized by the liver and small intestine.ApoA Ⅱ in human plasmaBiological half-life4.4 days.
3、 ApoA Ⅳ
ApoA Ⅳ is an apolipoprotein first found in rat HDL and CM. In 1979, Beisiegel et al confirmed that ApoA Ⅳ also exists in human plasma, mainly distributed in the part with density greater than 1.211g/ml.There are 376 mature ApoA ⅣAmino acid residueform.SDS-PAGE confirmed that the molecular weights of rat and human ApoA Ⅳ were 44000 and 46000 Da.Human and ratamino acid compositionSimilar is a kind ofglycoprotein, containing 6%carbohydrate, wheremannose1.8%,Galactose1.55%,N-acetylglucosamine1.55% andsialic acidAccounting for 1.1%.ApoA Ⅳ protein has polymorphism, and the biological half-life is 10h.The physiological function of ApoA Ⅳ is still unclear, and it is speculated that it is in HDLReverse transshipmentIt plays an important role in the process.In 1985, Steinmetz et al reported that ApoA Ⅳ could promote LCATcholesterolesterification。Goldberg reported that ApoA Ⅳ has been regulatedLipoprotein lipaseOfActivationAnd presumably promote the release of ApoA Ⅳ from HDL and VLDL.ApoA Ⅳ is synthesized by the liver and small intestine.[2]
Reasons for low
Apolipoproteins arePlasma LipoproteinThe important components of apolipoprotein a1 can be divided into five categories: a, b, c, d and e, and each category can be subdivided into several subclasses. Apolipoprotein a1 is a classification type of apolipoprotein.Apolipoprotein a1 is mainly used to carry lipids and stabilize the structure of lipoproteins. It also plays a role in promoting the transport of lipids, regulating enzyme activities, and guiding plasma lipoproteins to interact withCell surface receptorCombination and other important roles.
The reason of low apolipoprotein a1
The main reason for the low level of apolipoprotein a1 is the impairment of liver function. The decrease of apolipoprotein a1 synthesis by hepatocytes results in the low level of apolipoprotein a1 in the blood.Low apolipoprotein a1 is common in patients withatherosclerosis, diabetesHyperlipoproteinemiaAnd other diseases.
Reasons for high
1. Take someAntiepileptic drugsIt will cause high apolipoprotein a1. If the drug is stopped, it will return to normal;
2. Long term excessive drinking will lead to high apolipoprotein a1. At this time, you must stop drinking. If you do not drink in the future, apolipoprotein a1 willReturn to normal；
3. During pregnancy, apolipoprotein a1 is also higher, which is a normal physiological phenomenon;
4. Abnormal liver, withchronic hepatitisIt will cause high apolipoprotein a1, which is easy to be converted intocirrhosis。[3]
The age of 20-60 years old increases by about 20%, and obesity (weight overload) increasesLuteinizing hormoneIt can increase the result by about 19%.
Reduce exercise by about 2%, vegetarian diet by about 2%, and hypolipidemia by about 10%estrogenAt that time, it was reduced by about 6% (some people also reported that it was reduced by 30%). Many therapeutic drugs, such as:Cholagogue(No impactVLDL）, antominnicotinic acid, DextrothyroxineAsparaginaseCan lead toApolipoprotein BReduction of.
