Aminopeptidase structure

J Grembecka, A Mucha, T Cierpicki, P Kafarski (2003) The most potent organophosphorus inhibitors of leucine aminopeptidase Structure-based design, chemistry, and activity, J Med Chem 46(13) 2641—2655... 

It was clear for some time that a number of zinc enzymes required two or more metal ions for full activity, but in the absence of X-ray structural data the location of these metal centres with regard to one another was often uncertain. When the first 3-D structures began to appear, it became clear that the metals were in close proximity. A particular feature of many of these enzymes was the presence of a bridging ligand between two of the metal sites, usually an Asp residue of the protein, which is occasionally replaced by a water molecule. While some of the sites contain only Zn ions, several contain Zn in combination with Cu (in cytosolic superoxide dismutases) Fe (in purple acid phosphatases) or Mg (in alkaline phosphatase and the aminopeptidase of lens). 

Figure 15.13 Structure of the bimetallic core of K coli methionine aminopeptidase. (From Kobayashi and Shimizu, 1999. Reproduced with permission of Blackwell Publishing Ltd.)...

Goettig, P., Geoll, M., Kim, J.-S., Huber, R., and Beandstettee, H. Crystal structures of the tricorn interacting aminopeptidase FI with various ligands reveal its catalytic mechanism. EMBO J. 2002, 21. 

These proteolytic enzymes are all endopeptidases, which hydrolyse links in the middle of polypeptide chains. The products of the action of these proteolytic enzymes are a series of peptides of various sizes. These are degraded further by the action of several peptidases (exopeptidases) that remove terminal amino acids. Carboxypeptidases hydrolyse amino acids sequentially from the carboxyl end of peptides. They are secreted by the pancreas in proenzyme form and are each activated by the hydrolysis of one peptide bond, catalysed by trypsin. Aminopeptidases, which are secreted by the absorptive cells of the small intestine, hydrolyse amino acids sequentially from the amino end of peptides. In addition, dipeptidases, which are structurally associated with the glycocalyx of the entero-cytes, hydrolyse dipeptides into their component amino acids. 

Liu S, Widom J, Kemp CW, Crews CM, Clardy J. (1998) Structure of human methionine aminopeptidase-2 complexed with fumagillin. Science 282 1324-1327. 

Fig. 36. The three-dimensional structure of the binuclear zinc cluster of leucine aminopeptidase, as determined by X-ray crystallographic methods (Burley etai, 1990 S. K. Burley and W. N. Lipscomb, personal communication).

De, A. Basak, P. Iqbal, J. Polyaniline Supported Cobalt Catalyzed One Pot Stereoselective Synthesis of the Structural Analogs of Aminopeptidase Inhibitor Bestatin, Tetrahedron Lett. 1997, 38, 8383. 

Most of the lysosomal proteases called cathepsins are small 20- to 40-kDa glycoproteins found in all animal tissues.313 Most are cysteine proteases which function best and are most stable in the low pH reducing environment of lysosomes. They resemble papain in size, amino acid sequence, and active site structures. Papain is nonspecific but most cathepsins have definite substrate preferences. Cathepsin B is the most abundant. There are smaller amounts of related cathepsins H (an aminopeptidase)314 and L315 and still less of cathepsins C, K, and others. Cathepsin B is both an endopep-tidase and an exopeptidase.316 It acts on peptides with arginine at either Pj or P2 but also accepts bulky hydro-phobic residues in Pj and prefers tyrosine at P3.317 Cathepsin S is less stable at higher pH than other cathepsins and has a more limited tissue distribution, being especially active in the immune system.318 319... 

X-ray crystallography of the 65-kDa form reveal a three-domain structure. The central domain varies among different strains and is probably involved in recognition and in binding to cell surface receptors.e h The toxin binds to a receptor, apparently an aminopeptidase N, after which the toxin is rapidly inserted into the membrane forming a 1- to 2-nm diameter pore. This leads to cell death.)... 

Reports relating to the quaternary structure of leucine aminopeptidases have appeared,1297,1298 including a preliminary X-ray study.1299 In the latter work at 2.2 A resolution a P6322 space group is revealed, the dimensions of the unit cell being a = 132 and c = 122 A, The asymmetric unit is a protomer of RMM 54 000. 

Matrixin is implicated in arthritis and invasive cancer. There are also aminopeptidases, specific for the N-termini of proteins, that are zinc proteases. One example, leucine aminopeptidase, has a complex hexameric structure, which is unusual for a protease.145... 

Various peptide Michael acceptors have been described as a new class of inactivators for cysteine proteases. 5-7 The carbonyl group of the scissile peptide bond in the substrate is replaced by a nucleophile trapping moiety such as a vinylogous structure. An amino acid vinyl sulfone, l-(methylsulfonyl)-4-phenylbut-l-en-3-amine [H2NCH(Bzl)CH=CHS02Me] and a dipeptide derivative, Gly-HNCH(Bzl)CH=CHS02Me have both been prepared as inhibitors of cysteine proteases, leucine aminopeptidase and dipeptidyl peptidase I, respectively.1 5 A series of peptide vinyl sulfones has been synthesized as potent inhibitors for different cysteine proteases. 1A8 ... 

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