scholarly journals SOME PROPERTIES OF AN ESTERASE DERIVED FROM PREPARATIONS OF THE FIRST COMPONENT OF COMPLEMENT

1957 ◽  
Vol 106 (2) ◽  
pp. 327-343 ◽  
Author(s):  
Oscar D. Ratnoff ◽  
Irwin H. Lepow
Keyword(s):  
Amino Acid ◽  
Human Serum ◽  
Hydrolytic Enzymes ◽  
Physiological Role ◽  
Amino Acid Esters ◽  
Synthetic Amino Acid ◽  
Early Hypothesis ◽  
Antigen Antibody ◽  
Acid Esters

Studies on an esterase derived from partially purified preparations of the first component of complement are described. The esterase hydrolyzed certain synthetic amino acid esters, among which N-acetyl-L-tyrosine ethyl ester was most susceptible. This was hydrolyzed maximally between pH 7.5 and 8.2, and at 41°C. The esterase could not be identified with other previously described hydrolytic enzymes. An esterase with similar properties could also be eluted from antigen-antibody aggregates which had been treated with serum. Human serum contained a heat-labile inhibitor of the esterase which could not be identified with any of the known components of complement. The esterase was also inhibited by certain reducing agents. The experiments described support the early hypothesis that complement exerts its action enzymatically, but the physiological role of the esterase derived from preparations of complement is not yet clear.

Incorporating Amino Acid Esters into Catalysts for Hydrogen Oxidation: Steric and Electronic Effects and the Role of Water as a Base

2012 ◽  
Vol 31 (19) ◽  
pp. 6719-6731 ◽  
Author(s):  
Sheri Lense ◽  
Ming-Hsun Ho ◽  
Shentan Chen ◽  
Avijita Jain ◽  
Simone Raugei ◽  
...  
Keyword(s):  
Amino Acid ◽  
Hydrogen Oxidation ◽  
Amino Acid Esters ◽  
Electronic Effects ◽  
Acid Esters

scholarly journals The structure and enzymic activities of the C1r and C1s subcomponents of C1, the first component of human serum complement

1977 ◽  
Vol 163 (2) ◽  
pp. 219-227 ◽  
Author(s):  
R B Sim ◽  
R R Porter ◽  
K B M Reid ◽  
I Gigli
Keyword(s):  
Amino Acid ◽  
Polypeptide Chain ◽  
Amino Acid Esters ◽  
Serine Proteinases ◽  
Terminal Amino Acid ◽  
Synthetic Amino Acid ◽  
Terminal Amino ◽  
The Difference ◽  
A Chain ◽  
Acid Esters

The subcomponents C1r and C1s and their activated forms C-1r and C-1s were each found to have mol.wts. in dissociating solvents of about 83000. The amino acid compositions of each were similar, but there were significant differences in the monosaccharide analyses of subcomponents C1r and C1s, whether activated or not. Subcomponents C1r and C1s have only one polypeptide chain, but subcomponents C-1r and C-1s each contain two peptide chains of approx. mol.wts. 56000 (“a” chain) and 27000 (“b” chain). The amino acid analyses of the “a” chains from each activated subcomponent are similar, as are those of the “b” chains. The N-terminal amino acid sequence of 29 residues of the C-1s “a” chain was determined, but the C-1r “a” chain has blocked N-terminal amino acid. The 20 N-terminal residues of both “b” chains are similar, but not identical, and both show obvious homology with other serine proteinases. The difference in polysaccharide content of the subcomponents C-1r and C-1s is most marked in the ‘b’ chains. When tested on synthetic amino acid esters, subcomponent C-1r hydrolysed both lysine and tyrosine ester bonds, but subcomponent C-1r did not hydrolyse any amino acid esters tested nor any protein substrate except subcomponent C1s. The lysine esterase activity of subcomponent C1s provides a rapid and sensitive assay of the subcomponent.

Destruction of intracellular and isolated Leishmania mexicana amazonensis amastigotes by amino acid amides

Parasitology ◽  
1988 ◽  
Vol 96 (2) ◽  
pp. 289-296 ◽  
Author(s):  
M. Rabinovitch ◽  
V. Zilberfarb
Keyword(s):  
Amino Acid ◽  
Methyl Ester ◽  
Methyl Esters ◽  
Hydrolytic Enzymes ◽  
Amino Acid Esters ◽  
Leishmania Mexicana ◽  
Acid Methyl ◽  
Hydrolysis Of ◽  
Acid Esters ◽  
Amino Acid Methyl Esters

SummaryL-amino acid esters such as leucine methyl ester (Leu-OMe) destroy Leishmania mexicana amazonensis amastigotes by a mechanism which may involve hydrolysis of the compounds by parasite enzymes. Moreover, several esters (e.g. Ile-OMe) prevent the killing of parasites by Leu-OMe, perhaps by inhibition of the hydrolytic enzymes. We show here that certain amino acid amides are also leishmanicidal. Killing of Leishmania within macrophages was assessed microscopically, and that of isolated amastigotes was measured by reduction of the tetrazolium MTT. Amino acid amides were generally less active than the methyl esters and several were more toxic to the macrophages, as determined by inspection of Giemsa-stained preparations. Ranks of activity of the amides on isolated amastigotes were Trp > Leu > Phe > Met > Tyr. The amides of Ala, Gly, Val, Ile, His and D-Leu were inactive. This pattern of activity is similar to that of amino acid methyl esters. Ile-NH2 and a few other amides protected intracellular as well as isolated parasites from killing by Leu-OMe. Conversely, Ile-OMe reduced the toxicity of Leu-NH2 for isolated amastigotes. None of the esters or amides assayed prevented the destruction of Leishmania by Trp-NH2. The results are compatible with the view that amino acid esters and amides may be recognized by the same or similar parasite enzymes.

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