Biomaterial Database

Chloride as allosteric effector of yeast aminopeptidase I. 1985

K H Röhm

Activation of yeast aminopeptidase I by chloride was studied by kinetic methods. Several effects contributed to overall activity enhancement: At low concentrations of Zn2+ (an essential component of aminopeptidase I) chloride increased the amounts of active enzyme by reducing the cooperativity of metal binding. In addition, substrate turnover was enhanced due to increased kcat and a moderate decrease of Km. At high concentrations of Zn2+ substrate saturation curves were sigmoidal. Under these conditions chloride activated by restoring Michaelis-Menten kinetics of substrate turnover. At the same time, reconstitution of active enzyme from apoprotein and Zn2+ was substantially accelerated and its inactivation due to loss of Zn2+ was retarded. Co2+-Substituted aminopeptidase I, although catalytically active, was much less sensitive to chloride activation. Apparent binding constants for chloride, as estimated from its effects on metal binding and catalysis, respectively, were different. This suggests that two independent activation mechanisms may be operative. Both appear to be mediated by conformational changes of the enzyme protein.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D002712	Chlorides	Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.	Chloride,Chloride Ion Level,Ion Level, Chloride,Level, Chloride Ion
D004789	Enzyme Activation	Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme.	Activation, Enzyme,Activations, Enzyme,Enzyme Activations
D006868	Hydrolysis	The process of cleaving a chemical compound by the addition of a molecule of water.
D000494	Allosteric Regulation	The modification of the reactivity of ENZYMES by the binding of effectors to sites (ALLOSTERIC SITES) on the enzymes other than the substrate BINDING SITES.	Regulation, Allosteric,Allosteric Regulations,Regulations, Allosteric
D000626	Aminopeptidases	A subclass of EXOPEPTIDASES that act on the free N terminus end of a polypeptide liberating a single amino acid residue. EC 3.4.11.	Aminopeptidase
D012441	Saccharomyces cerevisiae	A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.	Baker's Yeast,Brewer's Yeast,Candida robusta,S. cerevisiae,Saccharomyces capensis,Saccharomyces italicus,Saccharomyces oviformis,Saccharomyces uvarum var. melibiosus,Yeast, Baker's,Yeast, Brewer's,Baker Yeast,S cerevisiae,Baker's Yeasts,Yeast, Baker
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D015032	Zinc	A metallic element of atomic number 30 and atomic weight 65.38. It is a necessary trace element in the diet, forming an essential part of many enzymes, and playing an important role in protein synthesis and in cell division. Zinc deficiency is associated with ANEMIA, short stature, HYPOGONADISM, impaired WOUND HEALING, and geophagia. It is known by the symbol Zn.