PROLINE OXIDASES IN HANSENULA SUBPELLICULOSA

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Ling, Chung-Mei (Illinois Institute of Technology, Chicago), and L. R. Hedrick. Proline oxidases in Hansenula subpelliculosa. J. Bacteriol. 87:1462–1470. 1964—Cells of Hansenula subpelliculosa can use l-proline as a carbon and a nitrogen source after a 6- to 8-hr induction period. However, they cannot use l-glutamate as both nitrogen and carbon sources unless the induction period is of several days' duration. Two l-proline oxidases were demonstrated in the mitochondrial preparation of this yeast. One forms the product Δ′-pyrroline-2-carboxylic acid (P2C), which is in equilibrium with α-keto-δ-amino-valeric acid; the other forms the product Δ′-pyrroline-5-carboxylic acid (P5C), which is in equilibrium with glutamic-γ-semialdehyde. The first-mentioned enzyme is induced when l-proline is the carbon source; the second appears to be constitutive, and is probably associated with the use of l-proline as a nitrogen source. The P2C-forming enzyme is specific for the l isomer of proline, and is inactive against l-hydroxyproline. The enzyme activity is at its peak when the mitochondria are prepared from logarithmically grown cells, and is rapidly reduced after cells reach the stationary phase of growth. Kinetic studies with varying concentrations of substrate indicate a Michaelis-Menten constant of 2.45 × 10−2m. Paper chromatographic studies, chemical tests with H2O2, sensitivity to freezing, and spectral measurements indicate that proline oxidase from H. subpelliculosa mitochondria forms a product from l-proline which is like, if not identical to, P2C formed by the action of sheep kidney d-proline oxidase upon dl-proline. The soluble portion of the cell extract contains NAD+ enzymes which use either P2C (α-keto-δ-amino-valeric acid) or P5C (glutamic-γ-semialdehyde) as substrates. No glutamic dehydrogenase activity could be detected when l-glutamic acid and the nicotinamide adenine dinucleotide (NAD+) cofactor were added to the supernatant solution with the yeast enzymes. The presence of a dehydrogenase NAD+ enzyme for activity with P2C (α-keto-δ-amino-valeric acid) has not been previously reported.

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