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c. albicans is the most prevalent cause of hospital - acquired infectious fungal diseases . for the immunocompromised individual , this fungus causes life - threatening systemic diseases , and its mortality may be as high as 50% .
superficial fungal infections such as thrush and vaginitis are also caused by c. albicans [ 14 , 15 ] .
the secreted lipase activity of c. albicans was first detected by fu et al . .
a subsequent genomic library screening has identified the gene , lip1 that encodes a lipase containing the conserved gly - x - ser - x - gly motif . non - albicans candida spp . such as c. parapsilosis , c. tropicalis , and c. krusei
have also been shown to possess a gene that is orthologous to c. albicans lip1 .
the discovery of lip1 in c. albicans has led to the identification of additional 9 lipase - encoding genes , lip2~lip10 , wherein the sequence is highly conserved ( up to 80% sequence identity ) .
the contribution of the lipase to c. albicans persistence and virulence has also been suggested , based on the observation of expression of all 10 lipases during the yeast - hypha transition and the detection of transcription of lipases such as lip5 , lip6 , lip8 , and lip9 during experimental infections .
the differential expression of lip1~lip10 during colonization in experimental models and in patient specimens has also been previously reported [ 17 , 18 ] .
furthermore , an additional ~70 kda extracellular lipase activity has been detected and shown to exert cytotoxic effects in the host macrophages and hepatocytes , presumably through the production of reactive oxygen species [ 19 , 20 ] .
extracellular phospholipases also play major roles in the virulence of c. albicans , and a previous study has shown that approximately 79% of clinically isolated c. albicans strains secrete the enzyme .
pla , plb , plc , and pld have been detected in c. albicans , and the genes encoding these proteins have been identified [ 22 - 26 ] .
a strain lacking plb1 has been generated and used in the assessment of the virulent attributes of plb .
although plb1 did not influence the growth and morphology of the fungus or its adherence to the host cell , the virulence of the null mutant was significantly attenuated in murine models of disseminated candidiasis [ 24 , 27 ] . the second gene , plb2 , which encodes for plb , has also been identified in c. albicans .
however , its role may be marginal , because in vivo analysis of 137 human subjects with oral and vaginal candidiasis revealed that only plb1 but not plb2 expression correlates with human oral infections . to date , 3 genes , plc1 , plc2 , and plc3 , which encode plc , have been identified in c. albicans . among these
although the heterozygous plc1/plc1 mutant and the mutant lacking plc2 and plc3 were deficient in hyphal formation , the functions of plc were shown to be dispensable for virulence .
pld is involved in diverse essential cellular processes , including sporulation , growth , and membrane lipid synthesis in the non - pathogenic model yeast saccharomyces cerevisiae [ 31 - 34 ] .
relevant roles for pld in c. albicans have been previously demonstrated by mclain and dolan , and the gene encoding the protein with a highly conserved pld motif was identified and designated as pld1 .
an attenuation of virulence was observed in mice orally infected with a pld1-deficient mutant , thus suggesting that pld may play a role in the pathogenesis of c. albicans .
accumulating data therefore indicate that lipolytic enzymes , such as lipases and phospholipases , play critical roles in virulence of c. albicans .
c. neoformans is an encapsulated human pathogenic fungus that causes pulmonary cryptococcosis and cryptococcal meningitis mainly in immunocompromised individuals such as acquired immunodeficiency syndrome ( aids ) patients [ 37 , 38 ] . to date , little information on the functions and the roles of lipases in c. neoformans is available , although genome sequence data have indicated that the fungus possesses at least 3 lipase genes . unlike c. albicans , none of the lipase - encoding genes in c. neoformans produce a protein with a signal peptide and no extracellular lipase activity has been detected from a clinically isolated c. neoformans strain . in contrast ,
numerous studies have suggested that phospholipases play a role in the physiology and virulence of c. neoformans .
early studies have reported that clinically isolated c. neoformans strains secrete phospholipases , and a characterization of their activity has identified these as mainly phospholipase b and suggested that the activity of this enzyme correlates with the capsule size and virulence of the fungus [ 40 - 42 ] .
phospholipase a activity has also been previously reported , although the gene encoding this particular enzyme and its virulence attributes have not been established [ 43 , 44 ] .
the gene encoding phospholipase b , plb1 , has been identified and a deletion mutant has been generated through targeted gene disruption .
the plb1 mutant displayed no particular phenotype when it was examined for the expression of major virulence factors such as the ability to grow at 37 , capsule formation , and melanin synthesis .
however , deletion of plb1 resulted in attenuated virulence in the mouse inhalation model and the rabbit meningitis model , indicating that plb contributes to the pathogenicity of c. neoformans .
the importance of plb in the virulence of c. neoformans was further confirmed by the observation of glycerophosphorylcholine ( gpc ) in lesions extracted from animals infected with c. neoformans .
the occurrence of gpc was consistent with the generation of hydrolysis products from the host phospholipids through the action of plb in c. neoformans .
furthermore , the study suggested that plb activity is required for the initiation of interstitial pulmonary infections and for the dissemination from the lung through the lymphatics and blood , whereas the dissemination of cryptococci to the central nervous system was shown to be independent of the enzyme . c. neoformans plb contains an n - terminal secretory leader peptide and acquires a glycosylphosphatidylinositol ( gpi ) anchor that facilitates its attachment to the plasma membrane prior to secretion .
plb in c. neoformans is also extensively glycosylated at its n - terminal , which influences membrane association and the secretion of the enzyme .
.   demonstrated that cleavage of plb is mediated by phosphatidylinositol - specific phospholipase c ( pi - plc ) , which is encoded by two genes , plc1 and plc2 .
the mutant that lacks either plc1 or plc2 was constructed to characterize the functions of pi - plc in c. neoformans .
while no particular phenotypic characteristic was observed in the plc2 mutant , the effect of the deletion of plc1 was dramatic .
the plc1 mutant showed an impaired growth at 37 , protein secretion , and melanin production , and was avirulent in a murine inhalation model of cryptococcosis . a correlation between plc and the protein kinase c / mitogen - activated protein kinase signaling pathway has also been suggested and
has further confirmed the significant roles of plc in the physiology and pathogenicity of c. neoformans .
malassezia spp . are associated with various dermatological diseases , including seborrheic dermatitis , dandruff , atopic dermatitis , and pityriasis versicolor . to date , 14 spp .
, except m. pachydermatis , are known to be obligatorily lipid - dependent . the lipophilic nature of malassezia spp . may be attributable to its inability to synthesize myristic acid , which is the precursor of long chain fatty acids .
recent genome analysis of m. globosa has revealed the absence of a gene that influences fatty acid synthesis .
the genome of m. globosa contains a number of genes that encode for lipolytic enzymes , including 14 lipases and 9 phospholipases , which may compensate for the lipid dependency of the fungus .
a significantly higher lipid content in the cell wall of malassezia spp . compared to non -
pathogenic fungi such as s. cerevisiae has been previously reported , and the lipid microfibrillar layer of the malassezia cell has been shown to down - regulate the inflammatory immune response , implying that the lipid dependency of the fungus might play a role in virulence [ 53 , 54 ] . the importance of the lipase function was first studied in m. furfur .
its enzyme activity was initially detected in the insoluble fraction of the cells , and its optimum ph was determined as acidic . a positive correlation between lipase activity and cell growth has also been observed .
brunke and hube   cloned and characterized the gene , mflip1 , which encodes for the extracellular lipase in m. furfur .
a protein sequence analysis has shown that mflip1 contains the conserved lipase motif , gly - x - ser - x - gly , and is similar to lipases in c. albicans .
the protein contains a signal peptide at its n - terminus , but not a transmembrane domain or a gpi - anchor motif .
the mflip1 gene might not belong to other lipase gene families in the genome of m. furfur , because no signal was detected during southern blot analysis by using the cdna fragment of the gene as a probe .
interestingly however , the same approach using the genome of m. pachydermatis displayed signals , thus suggesting the presence of an ortholog .
moreover , heterologous expression of the cdna of mflip1 in pichia pastoris has suggested that the recombinant mflip1 is most active at 40 and its optimal ph was 5.8 .
the gene encoding for the extracellular lipase in m. pachydermatis has been cloned and characterized .
m. globosa , one of the most frequently isolated malassezia spp . from patients with dandruff and seborrheic dermatitis , also displayed extracellular lipase activity .
although recent genome analysis has revealed there are at least 14 lipase - encoding genes , only one gene , mglip1 , has been identified .
, the protein product of mglip1 contains the conserved lipase motif and the signal peptide .
the regulation of gene expression has also been investigated , with mglip1 transcription levels regulated by its growth phase in vitro .
the expression of mglip1 was higher in the late log phase compared to early log and stationary phases .
moreover , the expression of mglip1 was detected in human scalp specimens , indicating that lipases may play a key role in virulence of m. globosa .
the structure of mglip1 has been proposed , and its substrates have been reported to be strictly specific for mono- and diacylglycerol , but not triacylglycerol [ 58 , 59 ] .
the enzyme has been designated as mglip2 and optimal activity has been observed at 30 and ph 5.0 .
interestingly , a recent study compared the extracellular lipase activity of several malassezia spp . , with m. globosa showing the highest lipase activity .
detected extracellular phospholipase activities in m. furfur , m. pachydermatis , m. slooffiae , m. sympodialis , m. globosa , m. restricta , and m. obtusa .
however , enzyme activity was higher only in m. pachydermatis , which is lipid - independent and has been normally isolated in dogs .
the phospholipase activity in malassezia spp . associated with humans is relatively low , which implies that the role of secreted phospholipases in malassezia spp
numerous experimental data have revealed the contribution of lipolytic enzymes in the virulence of human pathogenic fungi ( table 1 ) . c. albicans and c.
neoformans have served as good model systems for investigating the functions and roles of specific enzymes in fungal pathogenesis .
lipolytic enzymes , which include secreted lipases and phospholipases , have been shown to influence growth , morphology , adherence , and dissemination of fungal cells across the host .
several studies have also emphasized the significance of lipolytic enzymes in malassezia spp . , although no genetic tool has been developed .
therefore , a greater effort in understanding the roles of lipolytic enzymes in fungal pathogens is warranted .
pathogenic microbes secrete various enzymes with lipolytic activities to facilitate their survival within the host . 
 lipolytic enzymes include extracellular lipases and phospholipases , and several lines of evidence have suggested that these enzymes contribute to the virulence of pathogenic fungi . 
 candida albicans and cryptococcus neoformans are the most commonly isolated human fungal pathogens , and several biochemical and molecular approaches have identified their extracellular lipolytic enzymes . the role of lipases and phospholipases in the virulence of c. albicans has been extensively studied , and these enzymes have been shown to contribute to c. albicans morphological transition , colonization , cytotoxicity , and penetration to the host . while not much is known about the lipases in c. neoformans , the roles of phospholipases in the dissemination of fungal cells in the host and in signaling pathways have been described . 
 lipolytic enzymes may also influence the survival of the lipophilic cutaneous pathogenic yeast malassezia species within the host , and an unusually high number of lipase - coding genes may complement the lipid dependency of this fungus . 
 this review briefly describes the current understanding of the lipolytic enzymes in major human fungal pathogens , namely c. albicans , c. neoformans , and malassezia spp .