Leucine aminopeptidase and

Non-corrin cobalt has a number of interesting applications in the chemical industry, for example in the hydroformylation (OXO) reaction between CO, H2 and olefins. A number of non-corrin Co-containing enzymes have been described, including methionine aminopep-tidase, prolidase, nitrile hydratase and glucose isomerase. We describe the best characterized of these, namely the E. coli methionine aminopeptidase, a ubiquitous enzyme, which cleaves N-terminal methionine from newly translated polypeptide chains. The active site of the enzyme (Figure 15.13) contains two Co(II) ions that are coordinated by the side-chain atoms of five amino acid residues. The distance between the two Co2+ is similar to that between the two Zn2+ atoms in leucine aminopeptidase, and indeed the catalytic mechanism of methionine aminopeptidase shares many features with other metalloproteases, in particular leucine aminopeptidases. 

See Section IV.1 for alternative methods of chiral resolution. Partial chemical hydrolysis of proteins and peptides with hot 6 M HC1, followed by enzymatic hydrolysis with pronase, leucine aminopeptidase and peptidyl D-amino acid hydrolase, avoids racemiza-tion of the amino acids281. The problems arising from optical rotation measurements of chiral purity were reviewed. Important considerations are the nonideal dependence of optical rotation on concentration and the effect of chiral impurities282. 

The flavonoids fisetin and genistein exhibit antiangiogenic activity as evaluated in in vivo studies [279]. Flavonoids may also exert a limiting effect on tumor metastasis by way of their inhibitory activity on proteolytic enzymes such as trypsin, leucine aminopeptidase and other... 

Leucine Aminopeptidase and Other N-Terminal Exopeptidases Robert J. DeLange and Emil L. Smith... 

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 ... 

Found to be subject to metal ion catalysis, but the discovery by Kroll in 1952 that the hydrolysis af a-amino acid esters was catalyzed by metal ions stimulated considerable interest in the area. Many of these reactions can be considered as simple model systems for such metalloenzymes as arboxypeptidase A, leucine aminopeptidase and glycylglycine dipeptidase.25... 

Interestingly, compounds which have been investigated for their penetration-enhancing effect at the absorbing membrane have also been shown to decrease the metabolism of certain peptides. By denaturing leucine aminopeptidase and preventing enzyme-substrate complex formation, the bile salt sodium glycocholate has been shown to protect insulin from proteolysis in the rat nasal mucosa. 

Carmel, A., Kessler, E., and Yaron, A. 1977. Intramolecularly quenched fluorescent peptides as fluorogenic substrates of leucine aminopeptidase and inhibitors of clostridial aminopeptidase. Eur. J. Biochem. 73, 617-625. 

The effects of CPH-treatment of rats (1200 mg/ kg/d for 3d) on the polypeptide composition of renal brush border from the proximal tubule cells enzymatic activities and transport systems of the brush border membrane vesicles (BBMV) were investigated [77]. The results of these studies showed that CPH-treatment induces a 20-30% decrease in the specific activities of renal brush border enzymes leucine aminopeptidase and D-glutamyltransferase. SDS-gel electrophoresis showed that CPH-treatment induced a decrease of the intensity of 3 brush border polypeptides of molecular weights of 72,000, 58,000 and 39,000 [77]. 

Proximal tubule cells in culture should have retained functional attributes such as (1) polar architecture and junctional assembly of epithelia and correct membrane distribution of enzymes and transport systems (2) vectorial transport of solutes and water, manifested by the formation of domes when cultured on solid supports [81] and the generation of transepithelial electrophysiological properties [82, 83] due to the expression of proximal tubule specific claudins 2- and 10 [84, 85] (3) cellular uptake of xenobiotics from either the apical or basolateral side, as observed in vivo and (4) expression of nephron segment-specific characteristics, i.e., distinct expression of differentiation markers, metabolic and transport properties, and hormone responsiveness. Such markers include the expression of the brush border enzymes alkaline phosphatase, leucine aminopeptidase, and y-glutamyl transferase [4, 86], In addition, proximal tubule cells should possess Na+,K+-ATPase activities, Na+-dependent glucose, and p-aminohippurate transport. Proximal tubule cells increase cAMP levels in response to parathyroid... 

Koleva M (1977) Changes in the urinary excretion of gamma-glutamyltranspeptidase, leucine aminopeptidase and alkaline phosphatase in the combined action of ethylene glycol and high temperature. Probl Khig 3 35-46... 

B16. de Bersaques, J., Leucine aminopeptidase and naphthylamidases in human epidermis II. Biochemical and histochemical data in psoriasis and basaliomas. Arch. Klin. Exp. Dermatol. 234, 52-60 (1969). 

This mechanism may best be exemplified by metal-dependent proteases and peptidases such as thermolysin, leucine aminopeptidase, and carboxypeptidase A. Of these, the most systematic study of proton transfer has been conducted with ther-... 

Table 3 Enzymatic Parameters for L-Aminoacyl Prodrug as Substrates of Leucine Aminopeptidase and Half-Lives of L-Aminoacyl Prodrugs in the Human Plasma and Blood...

Disaccharidase, leucine aminopeptidase and glucose uptake in intestinalized gastric mucosa. Gastroenterology, 52 1137. 

Undisrupted rabbit liver lysosomes also catalyze the hydrolysis of substrates for leucine aminopeptidase and hexoseaminidase, but they do not hydrolyze benzyol-L-arginine- ff-naphthylamide (BANA), the classical substrate for cathepsin B, nor do they show any activity with substrates for 8-glucosidase (17). Thus the activities expressed by undisrupted lysosomes are restricted to those that are associated with the lysosomal membranes. The fact that the intralysosomal activities remain fully cryptic (e.g., for cathepsin B substrates) excludes the presence of disrupted or permeable lysosomes that might have accounted for the activities expressed by these lysosomal preparations. 

Two fractions, G-V and G-VI, which appeared to be homogeneous, were studied more closely. They were rechromatographed and the amino-acid composition, and N- and C-terminal amino acids were determined as shown in Table VII—3. Some amino-acid sequences in the N- and C-terminal regions have also been deduced from the results of digestion with leucine aminopeptidase and carboxypeptidase B followed by A, respectively. Further, tryptic, chymotryptic, and thermolytic peptides of fraction G-V have been investigated. 

The chemical structures of these peptides were established in the usual way by quantitative amino-acid analysis and sequence analysis by a combination of chemical and enzymic methods, including dinitrophenylation, dansylation, Edman degradation, hydrazinolysis and digestion with leucine aminopeptidase and carboxypeptidases A and B. The Neutral Protease peptides of the salmine and iridine components or derivatives thus identified are listed in Table VIII-6 with their recovery values. Differences in the amino-acid sequences and amounts of the peptides obtained from iridine I aroused the suspicion that two molecular species (a and b) were present in the iridine I component. This result, as already described, was supported by observations on the thermolysin peptides of iridine I. 

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