1.1 Introduction
1.1.1 Feature of ENO1
The taxonomic group of ENO1 exists in eukaryotes, including animals, fungi, plants, diatoms, apicomplexans and bacteria, including proteobacteria, actinobacteria and firmiccutes.
Enolase (2-phospho-D-glycerate hydrolyase; EC 4.2.1.11), encoded by
ENO1, is a phyllogentically conserved enzyme. It involved in both glycolysis
pathway (Fig. 1) and gluconeogenesis anabolic processes (Fig. 2), catalyzes the conversion of 2-phosphoglycerate to give phosphoenolpyruvate and the reverse reaction (Dinovo and Boyer, 1971; Stubbe and Abeles, 1980).1.1.1.1 ENO1 in vertebrate
Enolase of vertebrate is a dimer composed of 3 subunits, alpha, beta and gamma. α-Enolase is present in the liver as well as immature organs and localized to cytoplasm and cell membrane, while β-enolase is found in muscle tissue and the γ isozyme is neuronal-specific (Rider and Taylor, 1974; Fletcher et al., 1976; Jørgensen and Centervall, 1982; Cooper et al., 1984; Oliva et al., 1989). α-Enolase is encoded by ENO1. It can act as a plasminogen receptor to concentrate plasmin activity on the cell surface (Miles et al., 1991).
recruitment of inflammatory cells in tissue, and the formation of satellite-cell-dependent new myofiber (Diaz-Ramos et al., 2012). Interestingly, Wistow et al. showed α-enolase was present in embryonic duck lens, and that the cDNA encodes both α-enolase and lens τ-crystallin structural proteins (Wistow et al., 1988).
Giallongo et al. have addressed that the regulation of human α-enolase in response to heat shock induction and mitogenic stimulation of peripheral blood lymphocytes (Giallongo et al., 1986), and they also found the putative promoter region of α-enolase exist several SP1 binding sites and high content of G+C (Giallongo et al., 1990). The posttranslational modifications of α-enolase related to Alzhemer’s disease through multiple functions have been reported, and upregulation of α-enolase has been found in cardiac infarction (Takei et al., 1991; Nakajima et al., 1994; Castegna et al., 2002; Butterfield and Lange, 2009;
Diaz-Ramos et al., 2012). α-Enolase detected on the cell surface of cholangiocarcinoma may associate tumor cell invasion (Yonglitthipagon et al., 2012).
1.1.1.2 ENO1 in plant
The literature pictured enolase in plant as follows. In castor bean (Ricinus
communis cv. Hale), induction of enolase was unaffected by gibberellin A 3
(González and Delsol, 1981). In tomato, the anaerobic induced was low in enolase activity that may be less in response to anaerobic stress, and enolase is not a heat shock inducible protein (Van der Straeten et al., 1991). InArabidopsis thaliana plants, Van der Straeten et al. suggested a substrate shuttle
replaced enolase for glycolysis in chloroplasts (Van der Straeten et al., 1991).Parbhakar et al. suggested ENO1 might be the only missing enzyme for a complete glycolysis within Arabidopsis plastids (Prabhakar et al., 2010). The salt stress induced increase in enolase activity and expression of mRNA, and
enolase transcripts increased during the induction of Crassulacean acid metabolism by temperature and anaerobic stresses in Mesembryanthemum
crystallium L. (Forsthoefel et al., 1995). Fox et al. suggested that enolase
expression may be related during later acclimation periods of anaerobic stress inEchinochloa phyllopogon, but higher enolase activity is in response to the
anoxic in Echinochloa crus-pavonis (Fox et al., 1995). Lal et al. pictured enolase involves in Zea mays roots during anaerobic stress (Lal et al., 1998).Voll et al. supposed that reduce enolase activity affects shikimate branch of aromatic amino acid biosynthesis pathway within the plastid in enolase antisense
Nicotiana tabacum (Voll et al., 2009).
1.1.1.3 ENO1 in Saccharomycetales
ENO1 in Saccharomycetales has been investigated in Debaryomycetaceae
and Dipodascaceae. Among them the Candida species includes C. albicans,Candida dubliniensis and Candida orthopsilosis etc. Enolase in S. cerevisiae
is expressed as isozymes by two genes, ENO1 and ENO2 (McAlister and Holland, 1982; Entian et al., 1987).1.1.1.4 ENO1 in Candida albicans
CaENO1 loci exist on chromosome 1 in C. albicans (Candida Genome
Database; CGD, http://www.candidagenome.org), the systematic name is orf19.395; and the second allele was orf19.8025. The protein sequence ofCaENO1 is 64.7% homologous to the Homo sapiens alpha-enolase (Fig. 3),
which is highly associated with tumor invasion of cholangiocarcinoma patients (Yonglitthipagon et al., 2012).The identified CaENO1 protein sequence within fungal genomes show
similarity with CTRG_03163 Candida tropicalis MYA-3404, 86.2% similarity with CPAR2_207210 Candida parapsilosis CDC317, 86.0% similarity with PGUG_04391 Candida guilliermondii ATCC6260, 85.6% similarity with CLUG_03897 Candida Iusitaniae ATCC 42720, 85.9% similarity with CORT_0A06360 Candida orthopsilosis Co 90-125, 77.1% similarity with CAGL0102486g
Candida glabrate CBS138,
85.8% similarity with LELG_00641 Lodderomyces elongisporus NRLL YB-4239, and 84.2% similarity with DEHA2G14058 Debaryomyces hansenii CBS767. The Multiple alignment result and phylogenetic tree view align protein sequences of ENO1 relate to Homo sapiens and Saccharomycetales species by COBALT multiple aligment tool showed in Fig. 4 and Fig. 5. The C. albicans enolase also showed 76.4% sequence identity with S. cerevisiae YGR254W ENO1, and 74.5% with YHR174W ENO2.The 1323 bp cDNA encoding 440 amino acids of CaENO1 was similar to that of S. cerevisiae, and both have been found to be the most abundant proteins in the cell of which the expression was controlled by transcriptional modulators of controlling multiple genes (Maitra et al., 1971; Sundstrom and Aliaga, 1992).
Sundstrom and Aliaga presented the structural differences between C. albicans and S. cerevisiae, where the CaEno1 contain no cysteine residues, and a two-amino-acid insertion in the main domain (Sundstrom and Aliaga, 1992).
Early studies have shown that there are abundant enolase in the blood of candidiasis patients and it is useful as a marker of internal infection (Walsh et al., 1991). Sundstrom and Aliaga indicated that cell extracts comprised 0.7% and 2.0% of enolase in the yeast and hyphal forms of C. albicans, respectively.
Further, CaENO1 is a marker for disseminated candidiasis and may be the antigen to the selective stimulation of host responses when the host encounters fungal infection (Sundstrom and Aliaga, 1992; Sundstrom and Aliaga, 1994).
Postlethwait and Sundstrom showed that the carbon sources for propagating the cell perhaps modulate CaENO1 mRNA levels and suggested enolase or other
glycolytic enzymes might be useful antifungal targets (Postlethwait and Sundstrom, 1995). Martínez-Gomariz et al. showed CaENO1 expression is reduced after both ethanol and glucose are used in cellular respiration, and
CaENO1 less is abundant in the planktonic yeast cells than in hyphae and
biofilms (Martínez-Gomariz et al., 2009). In addition, Shirtliff et al.demonstrated that enolase is down-regulated when C. albicans is exposed to farnesol (Shirtliff et al., 2009). Bharucha et al. suggested that CaENO1 in RAM (Regulation of Ace2 and Morphogenesis) pathway mutants (cbk1/CBK1