Antifungal activity of cinnamic acid derivatives involves inhibition of benzoate 4-hydroxylase (CYP53).

AIMS: CYP53A15, from the sorghum pathogen Cochliobolus lunatus, is involved in detoxification of benzoate, a key intermediate in aromatic compound metabolism in fungi. Because this enzyme is unique to fungi, it is a promising drug target in fungal pathogens of other eukaryotes. METHODS AND RESULTS: In our work, we showed high antifungal activity of seven cinnamic acid derivatives against C. lunatus and two other fungi, Aspergillus niger and Pleurotus ostreatus. To elucidate the mechanism of action of cinnamic acid derivatives with the most potent antifungal properties, we studied the interactions between these compounds and the active site of C. lunatus cytochrome P450, CYP53A15. CONCLUSION: We demonstrated that cinnamic acid and at least four of the 42 tested derivatives inhibit CYP53A15 enzymatic activity. SIGNIFICANCE AND IMPACT OF THE STUDY: By identifying selected derivatives of cinnamic acid as possible antifungal drugs, and CYP53 family enzymes as their targets, we revealed a potential inhibitor-target system for antifungal drug development.

Expression of human lymphotoxin alpha in Aspergillus niger.

A gene-fusion expression strategy was applied for heterologous expression of human lymphotoxin alpha (LTalpha) in the Aspergillus niger AB1.13 protease-deficient strain. The LTalpha gene was fused with the A. niger glucoamylase GII-form as a carrier-gene, behind its transcription control and secretion signals. Special attention was paid to the influence of different codon usage on secretion of protein. In the case of human tumor necrosis factor alpha (TNFalpha) a dramatic change of secretion has been observed when human cDNA sequence was used instead of synthetic E. coli biased codons. In the case of LTalpha such a change of codon usage brought improvement at the RNA level, however, no increase in the quantity of secreted protein was observed, due to the proteolitic activity of the host organism. The estimated yield of secretion of LTalpha from A. niger into the soya medium was 50 pg l(-1) of culture.

Expression of catalytic subunit of bovine enterokinase in the filamentous fungus Aspergillus niger.

The cDNA encoding for catalytic subunit of bovine enterokinase (EK(L)), to which the sequence for Kex2 protease cleavage site was inserted, was expressed in the protease deficient filamentous fungus Aspergillus niger AB1.13. Fungal transformants were obtained in which expression of the glucoamylase fusion gene resulted in secretion of the protein into growth medium. Fusion polypeptide was processed to mature EK(L) by endogenous Kex-2 like protease cleavage during secretory pathway. The highest quantity of EK(L), up to 5 mg l(-1), was obtained in soya milk medium. The secreted EK(L) was easily purified from other proteins found in A. niger culture supernatant, using ion exchange and affinity chromatography. The yield of the purified and highly active EK(L) was 1.9 mg l(-1) of culture.

Can hTNF-alpha be successfully produced and secreted in filamentous fungus Aspergillus niger?

A gene-fusion expression strategy was applied for the heterologous expression of hTNF-alpha in A. niger AB1.13. The TNF-alpha gene was fused with the A. niger glucoamylase GII form as a carrier-gene, behind its transcription control and secretion signal. The protein was expressed in the cells in the form of a glucoamylase-fusion protein, but was not present in the culture medium. From the expression of two hTNF-alpha analogues, LK 811 (Cys95/148) and LK 802 (Cys95/148, His107/108) respectively, we concluded that oligomerisation was not the critical point for secretion of hTNF-alpha in A. niger, but more probably improper folding already at the stage of monomer formation, or even incorrect processing of the molecule during the secretion pathway.