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首页> 外文期刊>American Journal of Physiology >Ontogeny of carnitine biosynthesis in Sus scrofa domesticus, inferred from γ-butyrobetaine hydroxylase (dioxygenase) activity and substrate inhibition
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Ontogeny of carnitine biosynthesis in Sus scrofa domesticus, inferred from γ-butyrobetaine hydroxylase (dioxygenase) activity and substrate inhibition

机译：Ontogeny of carnitine biosynthesis in Sus scrofa domesticus, inferred from γ-butyrobetaine hydroxylase (dioxygenase) activity and substrate inhibition

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Lin X, Lyvers Peffer PA, Woodworth J, Odle J. Ontogeny of carnitine biosynthesis in Sus scrofa domesticus, inferred from γ-butyrobetaine hydroxylase (dioxygenase) activity and substrate inhibition. Am J Physiol Regul Integr Comp Physiol 319: R43-R49, 2020. First published May 20, 2020; doi:10.1152/ajp-regu.00051.2020.—γ-Butyrobetaine hydroxylase (γ-BBH) is the last limiting enzyme of the L-carnitine biosynthesis pathway and plays an important role in catalyzing the hydroxylation of γ-butyrobetaine (γ-BB) to L-carnitine. To study the developmental effect of substrate concentration on the enzyme's specific activity, kinetics of γ-BBH were measured in liver and kidney from newborn and 1-, 7-, 21-, 35-, 56-, and 210-day-old domestic pigs. Fresh tissue homogenates were assayed under nine concentrations of γ-BB from 0 to 1.5 mM. Substrate inhibition associated with age was observed at ≥0.6 mM of γ-BB. Hepatic activity was low at birth but increased after 1 day. By 21 days, the activity rose by 6.6-fold (P < 0.05) and remained constant after 56 days. Renal activity was higher than in liver at birth but remained constant through 35 days. By 56 days, the velocity increased by 44% over the activity at birth (P < 0.05). The apparent K_m for γ-BB at birth on average was 2.8-fold higher than at 1 day. The K_m value was 60% higher in kidney than liver during development but showed no difference in adult pigs. The total organ enzyme activity increased by 130-fold for liver and 18-fold for kidney as organ weight increased from birth to 56 days. In conclusion, age and substrate affect γ-BBH specific activity and K_m for γ-BB in liver and kidney. Whereas the predominant organ for carnitine synthesis is likely the kidney at birth, the liver appears to predominate after the pig exceeds γ days of age.

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