Determination of the Optimum pH for Isolation of a Compound with Multiple pKa's from Aqueous−Organic Solvent Mixtures

2001 ◽  
Vol 5 (1) ◽  
pp. 77-79 ◽  
Author(s):  
Louis S. Crocker ◽  
Yaling Wang ◽  
James A. McCauley
Keyword(s):  
Organic Solvent ◽  
Solvent Mixtures ◽  
Optimum Ph

New fluorogenic substrates for the determination of post-proline endopeptidase activity

1990 ◽  
Vol 55 (4) ◽  
pp. 1112-1118 ◽  
Author(s):  
Chryssa Tzougraki ◽  
George Kokotos ◽  
Hana P. Mašková ◽  
Eva Anzenbacherová ◽  
Tomislav Barth
Keyword(s):  
Enzyme Activity ◽  
Organic Solvent ◽  
Fluorogenic Substrate ◽  
Michaelis Constant ◽  
Fluorogenic Substrates ◽  
Endopeptidase Activity ◽  
Optimum Ph ◽  
Adverse Influence

A new fluorogenic substrate for determination of the activity of post-proline endopeptidase (EC 3.4.21.26), Z-Cys(Bzl)-Pro-NH-Meq has been synthesized. Affinity of this substrate to the enzyme was significantly higher than that of the hitherto employed substrates. The Michaelis constant of the post-proline endopeptidase for Z-Cys(Bzl)-Pro-NH-Meq was at the optimum pH (7.0) 1.05 10-6 mol l-1. The concentration of dimethylsulfoxide used for the solubilization of Z-Cys(Bzl)-Pro-NH-Meq (<0.4%) was outside the limits of adverse influence of the organic solvent on the enzyme activity. The fluorogenic substrate Z-Gly-Pro-NH-Meq was also synthesized for comparison (Km = 10.35 10-6 mol l-1 at pH 7.0).

Synthesis and use of an aminoquinolinone derivative for the fluorometric determination of oxytocinase

1989 ◽  
Vol 54 (10) ◽  
pp. 2802-2808 ◽  
Author(s):  
Hana P. Mašková ◽  
George Kokotos ◽  
Chryssa Tzougraki ◽  
Tomislav Barth
Keyword(s):  
Organic Solvent ◽  
Human Serum ◽  
Enzyme Reaction ◽  
Natural Substrate ◽  
Fluorogenic Substrate ◽  
Chromogenic Substrates ◽  
Michaelis Constant ◽  
Fluorometric Determination ◽  
Optimum Ph

A new fluorogenic substrate for the determination of the activity of human serum oxytocinase-cystine aminopeptidase (EC 3.4.11.3), H-Cys(Bzl)-NH-Meq, has been synthesized. The affinity of H-Cys(Bzl)-NH-Meq to oxytocinase was by two orders higher than that of the usually employed chromogenic substrates. The Michaelis constant of oxytocinase for this substrate was within the range of the optimum pH (7.0–7.5) 2.3.10-6 mol l-1, i.e. in the region of the affinity of the natural substrate, oxytocin. The concentration of dimethylsulfoxide used for the solubilization of H-Cys(Byl)-NH-Meq (<0.4%) did not influence adversely the course of the enzyme reaction as in the case of chromogenic substrates, where the concentrations of the organic solvent exceeded 3%.

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