scholarly journals Functional Analysis of Conserved Histidine Residues inCephalosporium acremoniumIsopenicillin N Synthase by Site-directed Mutagenesis

1996 ◽  
Vol 271 (2) ◽  
pp. 889-894 ◽  
Author(s):  
Doreen S. H. Tan ◽  
Tiow-Suan Sim
Keyword(s):  
Functional Analysis ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Histidine Residues

Site-directed mutagenesis and functional analysis of an active site tryptophan of insect chitinase

2002 ◽  
Vol 32 (11) ◽  
pp. 1477-1488 ◽  
Author(s):  
Hong Zhang ◽  
Xin Huang ◽  
Tamo Fukamizo ◽  
Subbaratnam Muthukrishnan ◽  
Karl J Kramer
Keyword(s):  
Functional Analysis ◽  
Active Site ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis

scholarly journals Identification by site-directed mutagenesis of three essential histidine residues in membrane dipeptidase, a novel mammalian zinc peptidase

1997 ◽  
Vol 326 (1) ◽  
pp. 47-51 ◽  
Author(s):  
Shoshana KEYNAN ◽  
Nigel M. HOOPER ◽  
Anthony J. TURNER
Keyword(s):  
Specific Activity ◽  
Mammalian Species ◽  
Competitive Inhibitor ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Renal Metabolism ◽  
Leukotriene D4 ◽  
Histidine Residues

Membrane dipeptidase (EC 3.4.13.19) is a plasma membrane zinc peptidase that is involved in the renal metabolism of glutathione and its conjugates, such as leukotriene D4. The enzyme lacks the classical signatures of other zinc-dependent hydrolases and shows no homology with any other mammalian protein. We have used site-directed mutagenesis to explore the roles of five histidine residues in pig membrane dipeptidase that are conserved among mammalian species. When expressed in COS-1 cells, the mutants H49K and H128L exhibited a specific activity and Km for the substrate Gly-D-Phe comparable with those of the wild-type enzyme. However, the mutants H20L, H152L and H198K were inactive, but were expressed at the cell surface at equivalent levels to the wild-type, as assessed by immunoblotting and immunofluorescence. These three mutants were compared with regard to their ability to bind to the competitive inhibitor cilastatin, which binds with equal efficacy to native and EDTA-treated pig kidney membrane dipeptidase. Expressed wild-type enzyme and mutants H20L and H198K were efficiently bound by cilastatin–Sepharose, but H152L failed to bind. Thus His-152 appears to be involved in the binding of substrate or inhibitor, whereas His-20 and His-198 appear to be involved in catalysis. Membrane dipeptidase shares some similarity with a dipeptidase recently cloned from Acinetobacter calcoaceticus. In particular, His-20 and His-198 of membrane dipeptidase are conserved in the bacterial enzyme, as are Glu-125 and His-219, previously shown to be required for catalytic activity.

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