Properties of Transaminases in Tissues of the Pear

Transaminases were first shown to be present in plant tissues by the early experiments of Virtanen and Laine (12), Albaum and Cohen (1), and Rautanen (9). In a later and more comprehensive paper Leonard and Burris (5) demonstrated transaminase activity in stem, leaf, and root tissues of numerous plant species. Wilson et al. (16) and Stumpf (11) further indicated the participation of plant enzymes in transaminations involving many amino and organic acids, while Schales and Schales (10) gave indirect evidence for the presence of transaminases in 42 different plants and plant organs. However, in spite of the apparent ubiquity of plant transaminases, their presence in tissues low in enzymatic proteins such as the flesh of many deciduous fruits has not been adequately substantiated. The experiments presented below have been undertaken to establish the presence of aspartatea-ketoglutarate (Asp-KG) and alaninea-ketoglutarate (Alan-KG) transaminase in pear flesh. Enzyme characteristics have also been investigated with the view of obtaining optimal assay conditions.