TY - JOUR
T1 - Hysteresis and positive cooperativity as possible regulatory mechanisms of Trypanosoma cruzi hexokinase activity
AU - Acosta, Héctor
AU - Cáceres, Ana
AU - González-Marcano, Eglys
AU - Quiñones, Wilfredo
AU - Avilán, Luisana
AU - Dubourdieu, Michel
AU - Concepción, Juan Luis
N1 - Copyright © 2015 Elsevier B.V. All rights reserved.
PY - 2014/12/1
Y1 - 2014/12/1
N2 - In Trypanosoma cruzi, the causal agent of Chagas disease, the first six or seven steps of glycolysis are compartmentalized in glycosomes, which are authentic but specialized peroxisomes. Hexokinase (HK), the first enzyme in the glycolytic pathway, has been an important research object, particularly as a potential drug target. Here we present the results of a specific kinetics study of the native HK from T. cruzi epimastigotes; a sigmoidal behavior was apparent when the velocity of the reaction was determined as a function of the concentration of its substrates, glucose and ATP. This behavior was only observed at low enzyme concentration, while at high concentration classical Michaelis-Menten kinetics was displayed. The progress curve of the enzyme's activity displays a lag phase of which the length is dependent on the protein concentration, suggesting that HK is a hysteretic enzyme. The hysteretic behavior may be attributed to slow changes in the conformation of T. cruzi HK as a response to variations of glucose and ATP concentrations in the glycosomal matrix. Variations in HK's substrate concentrations within the glycosomes may be due to variations in the trypanosome's environment. The hysteretic and cooperative behavior of the enzyme may be a form of regulation by which the parasite can more readily adapt to these environmental changes, occurring within each of its hosts, or during the early phase of transition to a new host.
AB - In Trypanosoma cruzi, the causal agent of Chagas disease, the first six or seven steps of glycolysis are compartmentalized in glycosomes, which are authentic but specialized peroxisomes. Hexokinase (HK), the first enzyme in the glycolytic pathway, has been an important research object, particularly as a potential drug target. Here we present the results of a specific kinetics study of the native HK from T. cruzi epimastigotes; a sigmoidal behavior was apparent when the velocity of the reaction was determined as a function of the concentration of its substrates, glucose and ATP. This behavior was only observed at low enzyme concentration, while at high concentration classical Michaelis-Menten kinetics was displayed. The progress curve of the enzyme's activity displays a lag phase of which the length is dependent on the protein concentration, suggesting that HK is a hysteretic enzyme. The hysteretic behavior may be attributed to slow changes in the conformation of T. cruzi HK as a response to variations of glucose and ATP concentrations in the glycosomal matrix. Variations in HK's substrate concentrations within the glycosomes may be due to variations in the trypanosome's environment. The hysteretic and cooperative behavior of the enzyme may be a form of regulation by which the parasite can more readily adapt to these environmental changes, occurring within each of its hosts, or during the early phase of transition to a new host.
KW - Adaptation, Physiological
KW - Adenosine Triphosphate/metabolism
KW - Gene Expression Regulation, Enzymologic
KW - Glucose/metabolism
KW - Glycolysis
KW - Hexokinase/metabolism
KW - Kinetics
KW - Trypanosoma cruzi/enzymology
U2 - 10.1016/j.molbiopara.2015.01.003
DO - 10.1016/j.molbiopara.2015.01.003
M3 - Article
C2 - 25683029
SN - 0166-6851
VL - 198
SP - 82
EP - 91
JO - Molecular and Biochemical Parasitology
JF - Molecular and Biochemical Parasitology
IS - 2
ER -