Acetylcholinesterase(AChE) | Butyrylcholinesterase (BuChE) |
Acetylcholinesterase (AChE), a serine hydrolase enzyme, is accountable for the hydrolysis of acetylcholine due to formation choline and acetate. This hydrolytic inactivation of acetylcholine serves as the physiologic mechanism for terminating its effects.  | A glycoprotein homotetramer that hydrolyses of choline esters to produce choline and a carboxylic acid.  |
ynonyme: Acetylcholine Acetylhydrolase,True Cholinesterase,Cholinesterase I. | Synonyme: Choline Esterase II, Pseudocholinesterase,Serine Cholinesterase. |
It is found in or attached to cellular or basement membranes of presynaptic cholinergic neurons and postsynaptic cholinoceptive cells. A soluble form occurs in cerebrospinal fluid and within cholinergic nerve terminals. | BuChE has a widespread distribution,being found in tissues such as liver,skin,brain & GIT smooth muscle & soluble form in the plasma. |
Hydrolysis of synthetic substrate butyrylcholine,as well as additional esters,such as procaine,succinylcholine & propanidid: More slowly than BuChE. | Hydrolysis of synthetic substrate butyrylcholine,as well as additional esters,such as procaine,succinylcholine & propanidid: More rapidly than AchE. |
AChE is selectively inhibited by BW284C51[1,5-bis(4-allyldimethyl-ammoniumphenyl)pentan-3-one dibromide,paraoxon or eserine. | BuChE is preferentially inhibited by iso-OMPA(tetraisopropylpyrophosphoramide),ethapropazine & quinidine. |
Hexokinase | Glucokinase |
In vertebrates, four major hexokinases are I, II, III, as well as IV or hexokinases A, B, C, and D. | Mammalian hexokinase IV, also termed to as glucokinase. |
Types I–III all have 100kD molecular weight. | It is monomeric having 50kD of molecular weight. |
All are sensitive to glucose 6 phosphate. Type III is inhibited by excess glucose. | Dissimilar than other members of the hexokinase family,it is not inhibited by the product of its reaction,glucose-6-phosphate.Glucokinase regulatory protein could inhibit glucokinase. |
Have low Km,high affinity for glucose.Vmax is high. | Has high Km,low affinity for glucose.Vmax is low. |
Location:in most tissue. | Location: β cells in pancrease & liver cells. |
Nucleotide means nitrogen base (purine or pyrimidine) + phosphate group + pentose sugar (ribose or deoxyribose)
They are elements of DNA.
Nucleoside= nitrogen base(purine or pyrimidine)+ pentose sugar(ribose or deoxyribose)
They are units of RNA.
the nitrogen bases (adenine,guanine etc.)combined with pentose sugar are called nucleoside.A nucleoside linked with a phosphate is called nucleotide.
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