Identification of thiamine monophosphate hydrolyzing enzymes in chicken liver

Copurification of chicken liver soluble thiamine monophosphatase and low molecular weight acid phosphatase

“…Step Volume, ml is very close to the kinetics observed in the crude extracts [17]. Table 2 shows the hydrolysis rates of various phosphate monoesters by the chicken liver enzyme.…”

“…The same values of kinetic parameters (K m = of 0.91 mM, V max = 8.1 µmol/min/mg) were also computed from the Hanes plot. It is to be noted, that the K m of the enzyme for ThMP in the chicken liver extract was evalua ted before to be 0.73 ± 0.02 mM [17]. Thus, in gene ral, the kinetic behavior of purified ThMPase…”

“…So the molecular nature of TMPase is currently unknown. In the search for an enzyme which would be a constituent of the intracellular thiamine metabolizing system in birds, we started studying some properties of ThMPase activity in chicken liver [17]. Two phosphatases were revealed to contribute to ThMP hydrolysis in liver homogenate.…”

“…It is only known that this compound could be a substrate for alkaline phosphatase (ALKP, EC 3.1.3.1) [13,14] and fluorideresistant (prostatic) acid phosphatase (PAP, EC 3.1.3.2) [15,16], both enzymes being membrane bound proteins. Quite recently, we have revealed a soluble ThMPase activity in chicken liver and hypothesized that this activity might belong to a low molecularweight acid phosphatase (LMWAP), also known as a lowmolecularweight protein phosphotyrosine phosphatase (LMWPTP) [17]. The present work is to study ThMPase subcellular distribution as well as to purify and characterize its basic properties in chicken liver.…”