Dissolved Organic Nitrogen Use by Phytoplankton: The Role of Cell-Surface Enzymes

Abstract

Some phytoplankton are able to use various forms of dissolved organic nitrogen without initial transport into the cell. Instead, these phytoplankton utilize cell-surface enzymes to degrade these forms of nitrogen to NH⁴₊ and several byproducts. Only the NH⁴₊ is then taken up. In the case of the cell-surface amino acid or amine oxidases, the by-products are hydrogen peroxide and an α-keto acid or aldehyde, respectively. The characteristics of these enzymes are discussed along with their possible importance in marine environments.

Keywords:

• Phytoplankton nutrition
• dissolved organic nitrogen
• cell-surface enzymes
• amino acid oxidases
• amine oxidases