This 1953 study investigated enzymes involved in ammonia production by four dermatophytic fungi: Microsporum canis, M. gypseum, Trichophyton rubrum, and T. mentagrophytes. Bentley grew these organisms in shaken culture to obtain submerged growth and examined their respiratory rates and enzymatic activities. Initial experiments revealed high endogenous respiration in mycelial cells that made substrate utilization difficult to assess. Using acetone powder preparations, the researcher detected weak oxidative deamination of amino acids, similar to levels in Penicillium chrysogenum. More significantly, she successfully extracted and characterized asparaginase from M. gypseum, demonstrating that the enzyme converts asparagine to aspartic acid and ammonia through simple hydrolysis. The asparaginase showed optimal activity at pH 8.5, required alkaline buffers for extraction, and demonstrated high substrate affinity with half-maximal velocity at approximately 0.001 M asparagine. The enzyme functioned both aerobically and anaerobically, suggesting a hydrolytic rather than oxidative mechanism.

Key findings

• Submerged cultures of dermatophytes showed high respiratory rates (7-12 μl O₂/hr/mg dry weight) with pronounced endogenous respiration unaffected by substrate addition
• Acetone powder preparations demonstrated weak oxidative deamination of amino acids, particularly aspartic acid, with activity similar to Penicillium chrysogenum
• Asparaginase was successfully extracted from M. gypseum and characterized with optimal pH of 8.5 and high substrate affinity (Km ~0.001 M)
• Asparaginase catalyzed simple hydrolysis of asparagine to aspartic acid and ammonia through a non-oxidative mechanism, functioning both aerobically and anaerobically