Glutamic Acid Decarboxylase in Sea Lamprey (Petromyzon marinus): Characterization, Localization, and Developmental Changes

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Abstract
Assays for glutamic acid decarboxylase (GAD) were determined in homogenates of brain and spinal cord from larval and adult sea lamprey (P. marinus). The enzyme had similar characteristics in both stages. Optimal pH was 6.8; optimal temperature was 27-30.degree. C; Km at 27.degree. C was 5 mM. GAD activity was distributed uniformly along the length of the spinal cord. Specific activities for the larval cord and brain were 26 and 63 nm CO2/mg protein/h respectively. The specific activities for the adult cord and brain were 29 and 236 nm CO2/mg protein per h, respectively. The activity of cord homogenates did not change significantly between larval and adult stages, but that of the brain increased about 4-fold.