Expression of elastinolytic activity among isolates in Aspergillus section flavi

A survey of the distribution of elastinolytic potential among 32 culture collection isolates of Aspergillus flavus. A. oryzae, A. parasiticus, A. sojae, A. nomius, and A. tamarii revealed this character to be highly conserved within Aspergillus Section Flavi. Furthermore, 144 isolates of A. flavus from environmental samples from six separate regions of the United States produced elastase on solid medium. Most previously described polymorphisms in elastinolytic potential were attributed to the toxicity of borate buffers. Replacement of borate with HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid) resulted in detection of elastase production on solid medium by all tested fungal isolates except two that had been in culture over 50 years. In liquid culture, only isolates of A. flavus, A. tamarii, and A. oryzae accumulated elastase activity. Although isoelectric focusing revealed only one isoform (pI 9.0) of elastase in these culture filtrates, elastinolytic activity in filtrates was partially inhibited by both 1,10-phenanthrolene (2 mM) and phenylmethylsulfonylfluoride (2 mM), suggesting the presence of both metallo and serine elastinolytic proteinases.