9.0) optimal pH, more than two pH units higher than that of vertebrate AANATs. Conclusions The substrate selectivity profiles of bfAANATα and δ' are relatively broad, including alkylamines, arylalkylamines and diamines, in contrast to vertebrate forms, which selectively acetylate serotonin and other arylalkylamines. Based on these features, it appears that amphioxus AANATs could play several roles, including detoxification and biogenic amine inactivation. The presence of seven AANATs in amphioxus genome supports the view that arylalkylamine and polyamine acetylation is important to the biology of this organism and that these genes evolved in response to specific pressures related to requirements for amine acetylation."/>
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Table 2 Acetylation activity measured in tissue homogenates from heads of B. lanceolatum

From: Evolution of AANAT: expansion of the gene family in the cephalochordate amphioxus

   blAANAT activity
(nmol/h/μg of total protein)
Time of day pH Endogenous substrate Exogenous + endogenous
substrates
Exogenous + endogenous
substrates
+ CoA-T
Midday 8.5 0.26 ± 0.15 0.68 ± 0.27 0.004 ± 0.002
Midnight   0.08 ± 0.08 0.05 ± 0.05 0.001 ± 0.001
Midday 9.5 0.29 ± 0.08 0.47 ± 0.17 0.004 ± 0.001
Midnight   Not detectable Not detectable Not detectable
  1. Comparison of samples collected during day and night. The exogenous substrate is 10 mM PEA; 1 mM CoA-T has been used for inhibition. Data are given as the mean ± S.E.M. (N = 3 to 6).