Proteolytic enzymes in Chlamydomonas I. A survey on the aminopeptidase pattern in asynchronous vegetative cells of Chlamydomonas reinhardii

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The supernatant of a crude extract from vegetative cells of Chlamydomonas reinhardii contains three different types of aminopeptidases. They are similar in their substrate specificities to the relative alanine speciflc aminopeptidases, the relative leucine specific aminopeptidases and the specific proline iminopeptidases described in many other systems. Relative alanine specific aminopeptidase which also cleaves N-terminal Lys and Leu residues has a molecular weight of 92,000 daltons and is inhibited by zinc and manganese ions. Relative leucine specific aminopeptidase shows high activity with N-terminal Phe besides Leu, and is capable of cleaving Tyr, Pro, and to a minor degree Ala. It has a molecular weight of 76,000 daltons. No effects on its activity were detected in the presence of divalent cations or chelating agents. The iminopeptidase specifically splits N-terminal Pro and has a molecular weight of about 255,000 daltons. All the enzymes show optimal activity at pH 8.0〜8.5. The two aminopeptidases can be separated from the iminopeptidase by ammonium sulfate solubilization and from each other by subsequent fractionation on DEAE-cellulose. Relative leucine specific activity appeared as a single enzyme in all the fractionation techniques used, but it gave two distinct bands when crude extracts were run on native polyacrylamide gels. Therefore, this enzyme may exist in multiple molecular forms.
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