Mammalian forebrain ketimine reductase identified as μ-crystallin; Potential regulation by thyroid hormones

André Hallen, Arthur J L Cooper, Joanne F. Jamie, Paul A. Haynes, Robert D. Willows

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Ketimine reductase (E.C. 1.5.1.25) was purified to apparent homogeneity from lamb forebrain by means of a rapid multi-step chromatography protocol. The purified enzyme was identified by MS/MS (mass spectrometry) as μ-crystallin. The identity was confirmed by heterologously expressing human μ-crystallin in Escherichia coli and subsequent chromatographic purification of the protein. The purified human μ-crystallin was confirmed to have ketimine reductase activity with a maximum specific activity similar to that of native ovine ketimine reductase, and was found to catalyse a sequential reaction. The enzyme substrates are putative neuromodulator/transmitters. The thyroid hormone 3,5,3′-l-triiodothyronine (T3) was found to be a strong reversible competitive inhibitor, and may have a novel role in regulating their concentrations. μ-Crystallin is also involved in intracellular T3 storage and transport. This research is the first to demonstrate an enzyme function for μ-crystallin. This newly demonstrated enzymatic activity identifies a new role for thyroid hormones in regulating mammalian amino acid metabolism, and a possible reciprocal role of enzyme activity regulating bioavailability of intracellular T3.

LanguageEnglish
Pages379-387
Number of pages9
JournalJournal of Neurochemistry
Volume118
Issue number3
DOIs
Publication statusPublished - Aug 2011

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Prosencephalon
Thyroid Hormones
Enzymes
Enzyme activity
Triiodothyronine
Chromatography
Metabolism
Escherichia coli
Biological Availability
Purification
Mass spectrometry
Neurotransmitter Agents
Transmitters
Mass Spectrometry
Sheep
ketimine reductase
crystallin mu
Amino Acids
Substrates
Research

Cite this

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title = "Mammalian forebrain ketimine reductase identified as μ-crystallin; Potential regulation by thyroid hormones",
abstract = "Ketimine reductase (E.C. 1.5.1.25) was purified to apparent homogeneity from lamb forebrain by means of a rapid multi-step chromatography protocol. The purified enzyme was identified by MS/MS (mass spectrometry) as μ-crystallin. The identity was confirmed by heterologously expressing human μ-crystallin in Escherichia coli and subsequent chromatographic purification of the protein. The purified human μ-crystallin was confirmed to have ketimine reductase activity with a maximum specific activity similar to that of native ovine ketimine reductase, and was found to catalyse a sequential reaction. The enzyme substrates are putative neuromodulator/transmitters. The thyroid hormone 3,5,3′-l-triiodothyronine (T3) was found to be a strong reversible competitive inhibitor, and may have a novel role in regulating their concentrations. μ-Crystallin is also involved in intracellular T3 storage and transport. This research is the first to demonstrate an enzyme function for μ-crystallin. This newly demonstrated enzymatic activity identifies a new role for thyroid hormones in regulating mammalian amino acid metabolism, and a possible reciprocal role of enzyme activity regulating bioavailability of intracellular T3.",
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Mammalian forebrain ketimine reductase identified as μ-crystallin; Potential regulation by thyroid hormones. / Hallen, André; Cooper, Arthur J L; Jamie, Joanne F.; Haynes, Paul A.; Willows, Robert D.

In: Journal of Neurochemistry, Vol. 118, No. 3, 08.2011, p. 379-387.

Research output: Contribution to journalArticleResearchpeer-review

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