Autocamtide-2-相關(guān)抑制肽，肉豆蔻?；姿狨ナ且环NCaM激酶II抑制劑，通過預(yù)處理阻斷體內(nèi)嗎啡尋求行為的恢復(fù)。它是自清-2-相關(guān)抑制肽的增強細(xì)胞滲透性衍生物。

Autocamtide-2-related inhibitory peptide, myristoylated acetate is a CaM kinase II inhibitor that blocks the reinstatement of morphine-seeking behavior in vivo by pretreatment. It is an enhanced cell-permeable derivative of autocamtide-2-related inhibitory peptide.

烷基化肽-說明

專肽生物可提供多肽烷基化修飾，增加多肽一端的疏水性，例如常見的C18，C16，C14，C12，以及C6等，也可根據(jù)客戶要求，接其他長度的烷基化鏈。

細(xì)胞穿膜肽-說明
      穿透細(xì)胞膜進入細(xì)胞內(nèi)是許多作用靶點在細(xì)胞內(nèi)的生物大分子發(fā)揮作用的先決條件，然而生物膜的生物屏障作用阻止了許多高分子物質(zhì)進入細(xì)胞內(nèi)，從而很大程度地限制了這些物質(zhì)在治療領(lǐng)域的應(yīng)用。因此，如何引導(dǎo)這些物質(zhì)穿透細(xì)胞膜是一個迫切需要解決的問題，目前介導(dǎo)生物大分子穿透細(xì)胞膜的方法主要包括細(xì)胞穿透肽（cell penetrating peptides，CPPs）、脂質(zhì)體、腺病毒、納米顆粒、影細(xì)胞等，而CPPs是一類以非受體依賴方式，非經(jīng)典內(nèi)吞方式直接穿過細(xì)胞膜進入細(xì)胞的多肽，它們的長度一般不超過30個氨基酸且富含堿性氨基酸，氨基酸序列通常帶正電荷。
      1型人免疫缺陷病毒轉(zhuǎn)錄激活因子TAT（human immunodeficiency virus-1 transcription activator， HIV-1 TAT）是第一個被發(fā)現(xiàn)的細(xì)胞穿透肽，它憑借一種無毒的、高效的方式進入細(xì)胞。
      細(xì)胞穿透肽（cell penetrating peptides，CPPs）的一個重要特點是可以攜帶多種不同大小和性質(zhì)的生物活性物質(zhì)進入細(xì)胞，包括小分子化合物、染料、多肽、多肽核酸（peptide nucleo acid, PNA）、蛋白質(zhì)、質(zhì)粒DNA、siRNA、200nm的脂質(zhì)體、噬菌體顆粒和超順磁性粒子等，這一性質(zhì)為其成為靶向藥物的良好載體提供了可能。
      CPPs作為載體的優(yōu)勢在于低毒性和無細(xì)胞類型的限制，盡管CPPs可輸送不同類型的物質(zhì)進入細(xì)胞，但其實際應(yīng)用多集中于寡肽、蛋白質(zhì)、寡聚核苷（oligonucleotides，ONs)或類似物的細(xì)胞轉(zhuǎn)運。

跨膜機理
不同的細(xì)胞穿透肽（CPP）跨膜機制不同，一個細(xì)胞穿透肽（CPP）的具體機制有賴于幾個參數(shù)，如分子大?。〝y帶物質(zhì)）、溫度、細(xì)胞類型和細(xì)胞內(nèi)外的穩(wěn)定性等。細(xì)胞穿透肽（CPP）進入細(xì)胞的具體機制目前還不清楚，比較流行的推測包括以下三種：
A: 倒置膠粒模型（inverted micelle model），CPPs通過細(xì)胞膜上磷脂分子的移動形成倒置膠粒結(jié)構(gòu)，而進入胞漿。
B: 直接穿透，即孔隙結(jié)構(gòu)模型 (pore formation model)，CPPs在細(xì)胞膜上組成跨膜的孔隙結(jié)構(gòu)而進入胞漿 。
C: 內(nèi)吞方式進行細(xì)胞攝取。
來源: Cell-penetrating peptides and their therapeutic applications, Victoria Sebbage, BioscienceHorizons, Volume 2, Number 1, March 2009.

細(xì)胞穿透肽 HIV TAT
      細(xì)胞穿透肽（如HIV TAT）可以以直接穿透和內(nèi)吞兩種方式進入細(xì)胞。HIV TAT或者簡單的多聚精氨酸可被設(shè)計作為有效的藥物載體，但CPP（如HIV TAT）是如何實現(xiàn)胞膜轉(zhuǎn)運，目前仍不清楚。
簡單的HIV TAT是如何促進象直接穿透和內(nèi)吞作用的入胞機制的呢？來自Gerard Wong實驗室的研究人員研究了在不同的條件下，HIV TAT是如何與細(xì)胞質(zhì)膜、細(xì)胞骨架、特異的胞膜受體相互作用，從而誘導(dǎo)了多重轉(zhuǎn)運途徑。

      有趣的是，TAT在不同條件下可與同一序列發(fā)生多種不同的反應(yīng)，因而與胞膜、細(xì)胞骨架、特異受體相互作用可產(chǎn)生多種轉(zhuǎn)運途徑。
      CPP的跨膜機制與多肽序列存在很敏感的關(guān)系，如果在一個純親水性的CPP中增加一個疏水殘基，就能徹底地改變其轉(zhuǎn)運機制，例如，最簡單的CPP原型-多聚精氨基（polyR），可以誘導(dǎo)細(xì)胞膜上形成跨膜的孔隙結(jié)構(gòu)。疏水氨基酸通過插入胞膜來形成正曲率，精氨酸可同時形成正曲率和負(fù)曲率，賴氨酸只能沿一個方向形成負(fù)曲率，這就意味著在精氨酸與賴氨酸/疏水物之間存在補償關(guān)系。
      如果疏水性有助于形成負(fù)高斯曲率（Gaussian curvature），那為什么TAT肽中的疏水含量相對較低呢？其原因是CPPs都是利用盡可能少的疏水基去形成saddle-splay curvature。序列上的差異很可能只會在膜上誘導(dǎo)短暫的類似孔隙的跨膜結(jié)構(gòu)，從而形成對CPP來說更短的孔隙壽命。由于CPP的氨基酸組成不同，TAT肽在有或無受體情況下都可以介導(dǎo)細(xì)胞內(nèi)吞作用。

     專肽生物提供各類細(xì)胞穿膜肽序列，部分由現(xiàn)貨，例如TAT，R8，R4等，具體可咨詢銷售人員。

Definition

Cell permeable peptides (CPPs) are carriers with small peptide domains that can freely cross cell membranes.  They are mainly used as carriers of proteins and nucleic acids into the cell1.

Discovery

The first CPP was discovered independently by two laboratories in 1988 when it was found that the trans-activating transcriptional activator (Tat) from Human Immunodeficiency Virus 1 (HIV-1) could be efficiently taken up from the surrounding media by numerous cell types in culture2. 

Structural Characteristics

CPPs typically have an amino acid composition containing either a high relative abundance of positively charged, cationic amino acids such as lysine or arginine, or have sequences that contain an alternating pattern of polar/charged amino acids and non-polar, hydrophobic amino acids3.  Some examples include: TAT peptide-YGRKKRRQRRR, lipid membrane translocating peptide-KKAAAVLLPVLLAAP and Antennapedia leader peptide-KKWKMRRNQFWVKVQRG.

Classification

Numerous CPPs have been identified to date and they belong to a wide variety of protein families. For example, some CPPs are amphipathic protein family members3.

Mode of action

CPPs enter the cell with their carrier by either of three mechanisms:  Direct delivery that involves energy independent entry of the CPPs in to the cell4, endocytosis where the cells take up the CPPs by imbibing them with their cell membranes5 and translocation through the formation of transient structures which is yet to be understood6. 

Functions

CPPs have found numerous applications in medicine as drug delivery agents in the treatment of different diseases including cancer, virus inhibitors, contrast agents for cell labeling a classical example is Green Fluorescent protein GFP, as MRI contrast agents, quantum dots7.  TAT is very effective in delivering drugs in vitro and in vivo and so far a peptide that matches its efficiency has not been found7.

References

1.     Wagstaff KM and David JA (2006). Protein Transduction: Cell Penetrating Peptides and Their Therapeutic Applications, Current Medicinal Chemistry, 13 (12), 1371-1387.

2.     Feng S and Holland EC (1988). HIV-1 Tat trans-activation requires the loop sequence within Tar. Nature 334, 165–167.

3.     Stewart KM, Horton KL, Kelley SO (2008). Cell-penetrating peptides as delivery vehicles for biology and medicine, Org Biomol Chem., 6(13), 2242-55.

4.     Luo D, Saltzman WM (2000). Synthetic DNA delivery systems. Nat. Biotechnol, 18, 33-37.

5.     Lundberg M., Wikstrom S and Johansson M (2003). Cell surface adherence and endocytosis of protein transduction domains, Mol. Ther., 8, 143–150.

6.     Deshayes S, Gerbal-Chaloin S, Morris MC, Aldrian-Herrada G, Charnet P, Divita G (2004). On the mechanism of non-endosomial peptide-mediated cellular delivery of nucleic acids, Biochim. Biophys. Acta, 1667, 141–147.

7.     Temsamani J and Vida P (2004). The use of cell-penetrating peptides for drug delivery, Drug Discovery Today, 9 (23), 1012-1019.

定義
酶是用于生化反應(yīng)的非常有效的催化劑。它們通過提供較低活化能的替代反應(yīng)途徑來加快反應(yīng)速度。酶作用于底物并產(chǎn)生產(chǎn)物。一些物質(zhì)降低或什至停止酶的催化活性被稱為抑制劑。
發(fā)現(xiàn)
1965年，Umezawa H分析了微生物產(chǎn)生的酶抑制劑，并分離出了抑制亮肽素和抗痛藥的胰蛋白酶和木瓜蛋白酶，乳糜蛋白酶抑制的胰凝乳蛋白酶，胃蛋白酶抑制素抑制胃蛋白酶，泛磷酰胺抑制唾液酸酶，烏藤酮抑制酪氨酸羥化酶，多巴汀抑制多巴胺3-羥硫基嘧啶和多巴胺3-羥色胺酶酪氨酸羥化酶和多巴胺J3-羥化酶。最近，一種替代方法已應(yīng)用于預(yù)測新的抑制劑：合理的藥物設(shè)計使用酶活性位點的三維結(jié)構(gòu)來預(yù)測哪些分子可能是抑制劑1。已經(jīng)開發(fā)了用于識別酶抑制劑的基于計算機的方法，例如分子力學(xué)和分子對接。
結(jié)構(gòu)特征
已經(jīng)確定了許多抑制劑的晶體結(jié)構(gòu)。已經(jīng)確定了三種與凝血酶復(fù)合的高效且選擇性的低分子量剛性肽醛醛抑制劑的晶體結(jié)構(gòu)。這三種抑制劑全部在P3位置具有一個新的內(nèi)酰胺部分，而對胰蛋白酶選擇性最高的兩種抑制劑在P1位置具有一個與S1特異性位點結(jié)合的胍基哌啶基。凝血酶的抑制動力學(xué)從慢到快變化，而對于胰蛋白酶，抑制的動力學(xué)在所有情況下都快。根據(jù)兩步機理2中穩(wěn)定過渡態(tài)絡(luò)合物的緩慢形成來檢驗動力學(xué)。
埃米爾•菲舍爾（Emil Fischer）在1894年提出，酶和底物都具有特定的互補幾何形狀，彼此恰好契合。這稱為“鎖和鑰匙”模型3。丹尼爾·科什蘭（Daniel Koshland）提出了誘導(dǎo)擬合模型，其中底物和酶是相當(dāng)靈活的結(jié)構(gòu)，當(dāng)?shù)孜锱c酶4相互作用時，活性位點通過與底物的相互作用不斷重塑。
在眾多生物活性肽的成熟過程中，需要由其谷氨酰胺（或谷氨酰胺）前體形成N末端焦谷氨酸（pGlu）。游離形式并與底物和三種咪唑衍生抑制劑結(jié)合的人QC的結(jié)構(gòu)揭示了類似于兩個鋅外肽酶的α/β支架，但有多個插入和缺失，特別是在活性位點區(qū)域。幾種活性位點突變酶的結(jié)構(gòu)分析為針對QC相關(guān)疾病5的抑制劑的合理設(shè)計提供了結(jié)構(gòu)基礎(chǔ)。
作用方式
酶是催化化學(xué)反應(yīng)的蛋白質(zhì)。酶與底物相互作用并將其轉(zhuǎn)化為產(chǎn)物。抑制劑的結(jié)合可以阻止底物進入酶的活性位點和/或阻止酶催化其反應(yīng)。抑制劑的種類繁多，包括：非特異性，不可逆，可逆-競爭性和非競爭性。可逆抑制劑 以非共價相互作用（例如疏水相互作用，氫鍵和離子鍵）與酶結(jié)合。非特異性抑制方法包括最終使酶的蛋白質(zhì)部分變性并因此不可逆的任何物理或化學(xué)變化。特定抑制劑 對單一酶發(fā)揮作用。大多數(shù)毒藥通過特異性抑制酶發(fā)揮作用。競爭性抑制劑是任何與底物的化學(xué)結(jié)構(gòu)和分子幾何結(jié)構(gòu)非常相似的化合物。抑制劑可以在活性位點與酶相互作用，但是沒有反應(yīng)發(fā)生。非競爭性抑制劑是與酶相互作用但通常不在活性位點相互作用的物質(zhì)。非競爭性抑制劑的凈作用是改變酶的形狀，從而改變活性位點，從而使底物不再能與酶相互作用而產(chǎn)生反應(yīng)。非競爭性抑制劑通常是可逆的。不可逆抑制劑與酶形成牢固的共價鍵。這些抑制劑可以在活性位點附近或附近起作用。
功能
工業(yè)應(yīng)用中， 酶在商業(yè)上被廣泛使用，例如在洗滌劑，食品和釀造工業(yè)中。蛋白酶用于“生物”洗衣粉中，以加速蛋白質(zhì)在諸如血液和雞蛋等污漬中的分解。商業(yè)上使用酶的問題包括：它們是水溶性的，這使得它們難以回收，并且一些產(chǎn)物可以抑制酶的活性（反饋抑制）。
藥物分子，許多藥物分子都是酶抑制劑，藥用酶抑制劑通常以其特異性和效力為特征。高度的特異性和效力表明該藥物具有較少的副作用和較低的毒性。酶抑制劑在自然界中發(fā)現(xiàn)，并且也作為藥理學(xué)和生物化學(xué)的一部分進行設(shè)計和生產(chǎn)6。
天然毒物 通常是酶抑制劑，已進化為保護植物或動物免受天敵的侵害。這些天然毒素包括一些已知最劇毒的化合物。
神經(jīng)氣體（ 例如二異丙基氟磷酸酯（DFP））通過與絲氨酸的羥基反應(yīng)生成酯，從而抑制了乙酰膽堿酯酶的活性位點。
參考
1、Scapin G (2006). Structural biology and drug discovery. Curr. Pharm. Des.,      12(17):2087–2097.
2、Krishnan R, Zhang E, Hakansson K, Arni RK, Tulinsky A, Lim-Wilby MS, Levy OE, Semple JE, Brunck TK (1998). Highly selective mechanism-based thrombin inhibitors:  structures of thrombin and trypsin inhibited with rigid peptidyl aldehydes. Biochemistry, 37 (35):12094-12103.
3、Fischer E (1894). Einfluss der configuration auf die wirkung der enzyme. Ber. Dt. Chem. Ges., 27:2985–2993.
4、Koshland DE (1958). Application of a theory of enzyme specificity to protein synthesis. PNAS., 44 (2):98–104.
5、Huang KF, Liu YL, Cheng WJ, Ko TP, Wang AH (2005). Crystal structures of human glutaminyl cyclase, an enzyme responsible for protein N-terminal pyroglutamate formation. PNAS., 102(37):13117-13122.
6、Holmes CF, Maynes JT, Perreault KR, Dawson JF, James MN (2002). Molecular enzymology underlying regulation of protein phosphatase-1 by natural toxins. Curr Med Chem., 9(22):1981-1989.

Definition
Enzymes are very efficient catalysts for biochemical reactions. They speed up reactions by providing an alternative reaction pathway of lower activation energy. Enzyme acts on substrate and gives rise to a product. Some substances reduce or even stop the catalytic activities of enzymes are called inhibitors.

Discovery
In 1965, Umezawa H analysed enzyme inhibitors produced by microorganisms and isolated leupeptin and antipain inhibiting trypsin and papain, chymostatin inhibiting chymotrypsin, pepstatin inhibiting pepsin, panosialin inhibiting sialidases, oudenone inhibiting tyrosine hydroxylase, dopastin inhibiting dopamine 3-hydroxylase, aquayamycin and chrothiomycin inhibiting tyrosine hydroxylase and dopamine J3-hydroxylase . Recently, an alternative approach has been applied to predict new inhibitors: rational drug design uses the three-dimensional structure of an enzyme's active site to predict which molecules might be inhibitors 1. Computer-based methods for identifying inhibitor for an enzyme have been developed, such as molecular mechanics and molecular docking.

Structural Characteristics
The crystal structures of many inhibitors have been determined. The crystal structures of three highly potent and selective low-molecular weight rigid peptidyl aldehyde inhibitors complexed with thrombin have been determined. All the three inhibitors have a novel lactam moiety at the P3 position, while the two with greatest trypsin selectivity have a guanidinopiperidyl group at the P1 position that binds in the S1 specificity site. The kinetics of inhibition vary from slow to fast with thrombin and are fast in all cases with trypsin. The kinetics are examined in terms of the slow formation of a stable transition-state complex in a two-step mechanism 2.

Emil Fischer in 1894 suggested that both the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.This is known as "the lock and key" model 3. Daniel Koshland suggested induced fit model where substrate and enzymes are rather flexible structures, the active site is continually reshaped by interactions with the substrate as the substrate interacts with the enzyme 4.

N-terminal pyroglutamate (pGlu) formation from its glutaminyl (or glutamyl) precursor is required in the maturation of numerous bioactive peptides. The structure of human QC in free form and bound to a substrate and three imidazole-derived inhibitors reveals an alpha/beta scaffold akin to that of two-zinc exopeptidases but with several insertions and deletions, particularly in the active-site region. The structural analyses of several active-site-mutant enzymes provide a structural basis for the rational design of inhibitors against QC-associated disorders 5.

Mode of Action
Enzymes are proteins that catalyze chemical reactions. Enzymes interact with substrate and convert them into products. Inhibitor binding can stop a substrate from entering the enzyme's active site and/or hinder the enzyme from catalyzing its reaction. There are a variety of types of inhibitors including: nonspecific, irreversible, reversible - competitive and noncompetitive. Reversible inhibitors bind to enzymes with non-covalent interactions like hydrophobic interactions, hydrogen bonds, and ionic bonds. Non-specific methods of inhibition include any physical or chemical changes which ultimately denature the protein portion of the enzyme and are therefore irreversible. Specific Inhibitors exert their effects upon a single enzyme. Most poisons work by specific inhibition of enzymes. A competitive inhibitor is any compound which closely resembles the chemical structure and molecular geometry of the substrate. The inhibitor may interact with the enzyme at the active site, but no reaction takes place. A noncompetitive inhibitor is a substance that interacts with the enzyme, but usually not at the active site.  The net effect of a non competitive inhibitor is to change the shape of the enzyme and thus the active site, so that the substrate can no longer interact with the enzyme to give a reaction. Non competitive inhibitors are usually reversible. Irreversible Inhibitors form strong covalent bonds with an enzyme.  These inhibitors may act at, near, or remote from the active site .

Functions
Industrial application, enzymes are widely used commercially, for example in the detergent, food and brewing industries. Protease enzymes are used in 'biological' washing powders to speed up the breakdown of proteins in stains like blood and egg. Problems using enzymes commercially include: they are water soluble which makes them hard to recover and some products can inhibit the enzyme activity (feedback inhibition) .

Drug molecules, many drug molecules are enzyme inhibitors and a medicinal enzyme inhibitor is usually characterized by its specificity and its potency. A high specificity and potency suggests that a drug will have fewer side effects and less toxic. Enzyme inhibitors are found in nature and are also designed and produced as part of pharmacology and biochemistry 6.

Natural poisons are often enzyme inhibitors that have evolved to defend a plant or animal against predators. These natural toxins include some of the most poisonous compounds known.

Nerve gases such as diisopropylfluorophosphate (DFP) inhibit the active site of acetylcholine esterase by reacting with the hydroxyl group of serine to make an ester.

References

Scapin G (2006). Structural biology and drug discovery. Curr. Pharm. Des.,      12(17):2087–2097.

Krishnan R, Zhang E, Hakansson K, Arni RK, Tulinsky A, Lim-Wilby MS, Levy OE, Semple JE, Brunck TK (1998). Highly selective mechanism-based thrombin inhibitors:  structures of thrombin and trypsin inhibited with rigid peptidyl aldehydes. Biochemistry, 37 (35):12094-12103.

Fischer E (1894). Einfluss der configuration auf die wirkung der enzyme. Ber. Dt. Chem. Ges., 27:2985–2993.

Koshland DE (1958). Application of a theory of enzyme specificity to protein synthesis. PNAS., 44 (2):98–104.

Huang KF, Liu YL, Cheng WJ, Ko TP, Wang AH (2005). Crystal structures of human glutaminyl cyclase, an enzyme responsible for protein N-terminal pyroglutamate formation. PNAS., 102(37):13117-13122.

Holmes CF, Maynes JT, Perreault KR, Dawson JF, James MN (2002). Molecular enzymology underlying regulation of protein phosphatase-1 by natural toxins. Curr Med Chem., 9(22):1981-1989.