Crypticity of Myrothecium verrucaria spores to maltose and induction of transport by maltulose, a common maltose contaminant.

Spores of the fungus Myrothecium verrucaria are cryptic to maltose and isomaltose. Induction of a transport system can be effected by several sugars whose order of effectiveness is: turanose > maltulose > sucrose > d-arabinose, d-fructose, nigerose, maltotriulose, kestose > melezitose, raffinose, nystose, and stachyose. The transport system is not specific to maltose and isomaltose, and it is apparently identical to an induced trehalose permease described previously. Induction of the permease is markedly influenced by spore age-older spores being more responsive. Pure maltose is not absorbed by spores. Absorption of commercial reagent-grade maltose is due to permease induction by maltulose as an impurity. Maltulose contamination of maltose was demonstrated by charcoal column chromatography and comparison of its physical, chemical, and permease-inductive properties with those of authentic maltulose. Maltose accumulates temporarily in spores after absorption and then decreases, although no conversion to glucose can be detected. Although spores contain small quantities of maltase, metabolism of maltose may be via some nonhydrolytic pathway.