TY - JOUR
T1 - Characterization and developmental regulation of tyramine-β-hydroxylase in the CNS of the moth, Manduca sexta
AU - Lehman, Herman K.
AU - Murgiuc, Cristina M.
AU - Hildebrand, John G.
N1 - Funding Information:
We thank Drs Stephen Carper, Norman Davis, and David Morton for helpful comments on the original manuscript, and Dr. A.A. Osman for insect rearing. This research was supported by grants from NIH (AI-23253 to JGH) and NSF (IBN-9496168 to HKL). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of the NIH or NSF.
PY - 2000/5
Y1 - 2000/5
N2 - Octopamine (OA) is present in insect nervous tissue, but little is known about its biosynthesis. In the CNS of Manduca sexta, OA levels increase markedly during postembryonic adult development. To study this increase, we developed an assay for tyramine-β-hydroxylase, the putatively rate-limiting enzyme for OA biosynthesis. Tyramine-β-hydroxylase activity in extracts of M. sexta CNS tissue: (1) was time- and protein-dependent, and with protein concentrations up to 2 μg/μl, was linear for 20 min; (2) had a pH optimum of 7.0 for conversion of tyramine to OA; (3) required ascorbate, copper, and catalase; and (4) had an apparent K(M, tyramine) of 0.22±0.04 mM. These characteristics resemble those of the mammalian enzyme dopamine-β- hydroxylase, suggesting that these two enzymes are functionally related. During adult development, tyramine-β-hydroxylase activity increased 11-fold in the brain and 9-fold in the abdominal ganglia, paralleling increases in OA levels in those CNS structures during metamorphosis. The apparent kinetic constants of tyramine-β-hydroxylase suggested that the amount of this enzyme present in the tissues increases. The increase in OA levels during adult development thus appears to be due to an increase in the level of enzyme available for OA synthesis and may reflect an increase in the number of octopaminergic neurons. (C) 2000 Published by Elsevier Science Ltd.
AB - Octopamine (OA) is present in insect nervous tissue, but little is known about its biosynthesis. In the CNS of Manduca sexta, OA levels increase markedly during postembryonic adult development. To study this increase, we developed an assay for tyramine-β-hydroxylase, the putatively rate-limiting enzyme for OA biosynthesis. Tyramine-β-hydroxylase activity in extracts of M. sexta CNS tissue: (1) was time- and protein-dependent, and with protein concentrations up to 2 μg/μl, was linear for 20 min; (2) had a pH optimum of 7.0 for conversion of tyramine to OA; (3) required ascorbate, copper, and catalase; and (4) had an apparent K(M, tyramine) of 0.22±0.04 mM. These characteristics resemble those of the mammalian enzyme dopamine-β- hydroxylase, suggesting that these two enzymes are functionally related. During adult development, tyramine-β-hydroxylase activity increased 11-fold in the brain and 9-fold in the abdominal ganglia, paralleling increases in OA levels in those CNS structures during metamorphosis. The apparent kinetic constants of tyramine-β-hydroxylase suggested that the amount of this enzyme present in the tissues increases. The increase in OA levels during adult development thus appears to be due to an increase in the level of enzyme available for OA synthesis and may reflect an increase in the number of octopaminergic neurons. (C) 2000 Published by Elsevier Science Ltd.
KW - Biogenic amines
KW - Dopamine-β-hydroxylase
KW - Insect
KW - Neurotransmitter synthesis
KW - Tyramine
KW - Tyramine-β- hydroxylase
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U2 - 10.1016/S0965-1748(00)00011-4
DO - 10.1016/S0965-1748(00)00011-4
M3 - Article
C2 - 10745161
AN - SCOPUS:0034059111
SN - 0965-1748
VL - 30
SP - 377
EP - 386
JO - Insect Biochemistry and Molecular Biology
JF - Insect Biochemistry and Molecular Biology
IS - 5
ER -