Prephenate aminotransferase, activity

A similar activity level was obtained in the deoxycholate, Triton X-100, and NP-40 extract preparations. Octyl glucoside and CHAPS extract preparations showed no detectable prephenate aminotransferase activity. When the hemoglobin step was used, there was no increase in the soluble activity recovered in the initial supernatant fraction, but the specific activity of the deoxycholate (the only detergent tried in this experiment) extract increased about tenfold. We would anticipate equally good results with use of Triton X-100 or NP-40 in combination with the hemoglobin step. 

The CM-1 and CM-2 isozymes of chorismate mutase in N. silvestris have been shown to exist in plastidial and cytosolic compartments. Similar evidence also exists in support of a parallel compartmentation of DAHP synthase isozymes, DAHP synthase-Mn being plastid-localized and DAHP synthase-Co being cytosolic (d Amato and Ganson, unpublished data), Prephenate aminotransferase activity of N. silvestris is also largely or entirely localized within plastids (d Amato and Bonner, unpublished data). 

Prephenate aminotransferase The specific activity of this enzyme in Supernatant I was 19.2 nmol/min/mg, and the total activity was retained in Supernatant II following centrifugation at 60,000g. The homogenized pellet (about 300 mg of protein) exhibited enzyme activity (specific activity of... 

Results similar to those obtained with shikimate dehydrogenase were obtained with prephenate aminotransferase (Fig. 7). High levels of enzyme activity that were present in stationary phase declined upon dilution into fresh medium, reaching a low point during exponential phase. 

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