Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.8 (phytase)
 1,997 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phytase is commonly used as a feed enzyme in monogastric animals to increase the bioavailability of phytate phosphorus and other nutrients. The accumulation of myo-inositol phosphate intermediates during phytate degradation in various segments of the gastrointestinal tract (GIT) is poorly understood. The aim of this study was to determine the efficacy of Buttiauxella spp. phytase in degrading the phytate in corn, soybean meal, and complete corn-soybean meal diet to myo-inositol phosphate esters (IP1-IP5) and completely dephosphorylated myo-inositol rings using an in vitro model of the poultry upper GIT. Our results show that the phytase hydrolyzes phytate efficiently to small IP esters, whereas the myo-inositol level remains constant between control and phytase treatments. Although the in vitro digestion model does not incorporate all factors that govern phytate hydrolysis, it is a valuable tool for evaluating phytase efficacy at various enzyme doses and with different feed ingredients.
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PMID:Effect of Phytase on in Vitro Hydrolysis of Phytate and the Formation of myo-Inositol Phosphate Esters in Various Feed Materials. 3153 68

Phytases are important commercial enzymes that catalyze the dephosphorylation of myo-inositol hexakisphosphate (phytate) to its lower inositol phosphate (IP) esters, IP6 to IP1. Digestion of phytate by Citrobacter braakii 6-phytase deviates significantly from monophasic Michaelis-Menten kinetics. Analysis of phytate digestion using isothermal titration calorimetry (ITC) using the single injection method produced a thermogram with two peaks consistent with two periods of high enzyme activity. Continuous-flow electrospray ionization time-of-flight mass spectroscopy (ESI-ToF-MS) provided real-time analysis of phytase catalysis. It was able to show that the first two cleavage steps were rapid and concurrent but the third cleavage step from IP4 to IP3 was slow. The third (IP4 to IP3), fourth (IP3 to IP2) and fifth (IP2 to IP1) cleavages were effectively sequential due to the preferred association of the more phosphorylated species with the phytase catalytic site. This created a bottleneck during the cleavage of IP4 to IP3 until the point at which IP4 was exhausted and was followed by the rapid cleavage of IP3 to IP2, which was observed as the second peak in the ITC thermogram. This work illustrates the importance of an orthogonal approach when studying non-specific or complex enzyme catalyzed reactions.
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PMID:Phytase catalysis of dephosphorylation studied using isothermal titration calorimetry and electrospray ionization time-of-flight mass spectroscopy. 3273 11