Mitochondria-bound hexokinase from rabbit reticulocytes is resistant to the inactivation induced by Fe(II)/ascorbate.
Exposure of rabbit reticulocytes to Fe(II)/ascorbate induced a pronounced decay in hexokinase activity. In reticulocytes, this enzyme is present in at least three different molecular forms, Ia, Ia* and Ib, sub-types of hexokinase type I, which show different intracellular distribution. Hexokinase Ia and Ib are soluble, whereas hexokinase Ia* is almost entirely bound to the mitochondria. Anion exchange chromatography of hexokinase from intact reticulocytes exposed to Fe(II)/ascorbate revealed a selective inactivation of forms Ia and Ib, whereas the form Ia* did not show any decay. Binding to the mitochondrial membrane seems to be responsible for the observed resistance of the form Ia* to the inactivation elicited by Fe(II)/ascorbate. Indeed, by using a cell-free system in which hexokinase Ia* was solubilized using Triton X-100, the decay in hexokinase activity induced by iron/ascorbate involved all three enzymatic forms.
Stocchi
V
V
Istituto di Chimica Biologica Giorgio Fornaini, Università di Urbino, Italy.
Fiorani
M
M
Biagiarelli
B
B
Piccoli
G
G
Saltarelli
R
R
Palma
F
F
Cucchiarini
L
L
Dachà
M
M
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001205:Ascorbic Acid / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D004789:Enzyme Activation / Q000187:drug effects*; D005296:Ferrous Compounds / Q000494:pharmacology*; D006593:Hexokinase / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology*; D007527:Isoenzymes / Q000737:chemistry; D008928:Mitochondria / Q000378:metabolism*; D017830:Octoxynol; D011817:Rabbits; D012156:Reticulocytes / Q000201:enzymology*; D012995:Solubility; D013997:Time Factors
D000970:Antineoplastic Agents; D005296:Ferrous Compounds; D007527:Isoenzymes; C051140:iron(II)-ascorbic acid complex; D017830:Octoxynol; D006593:Hexokinase; D001205:Ascorbic Acid