Subtilisin-γ-glutamyl transpeptidase: a novel combination as ungual enhancer for prospective topical application

A feather degrading strain of Bacillus licheniformis ER-15 was isolated which also degraded α-keratin of hooves. A detailed analysis revealed that a novel monomeric γ-glutamyl transpeptidase (GGT(30)), a proteolytic product of heterodimeric 67 kDa γ-glutamyl transpeptidase (GGT(67)), assists subtilisin during its action on α keratin. An equimolar combination of subtilisin and GGT(30) was designated as KerN and was used as ungual enhancer for topical application. KerN was effective in releasing proteins from nail plate surface and 300 µg of enzyme could release 41 µg protein/mg of nail after 24 h treatment. Scanning electron micrograph (SEM) revealed loosening of nail matrix confirming the action of KerN on nail keratin. Drug permeation studies revealed permeation of clotrimazole through both enzymatically pretreated nail plates and also through nail plates in presence of KerN. Nearly 58% drug could be retained by nail plates after 24 h of 300 µg/mL KerN which further enhanced up to 97% by prolonging the enzyme application. The enzyme was found to be stable in presence of drug even after 72 h. Thus, KerN can be used as an additive in formulation of topical drug for onchomycosis.