Chromosome 11 open reading frame 54 (C11orf54) is a protein that in humans is encoded by the C11orf54gene. The "Homo sapiens" gene, C11orf54 is also known as PTD012 and PTOD12. C11orf54 exhibits hydrolase activity on p-nitrophenyl acetate and acts on ester bonds, though the overall function is still not fully understood by the scientific community. The protein is highly conserved with the most distant homolog found is in bacteria.
The amino acid sequence contains the Domain of Uknown Function 1907. Found in this transcript is the HxHxxxxxxxxxH motif which coordinates the zinc ion involved in the hydrolase activity. An LR nest motif is found at lys262 and Arg263. The LR nest motif forms hydrogen bonds between the NH groups and anions; an acetate anion is coordinated with the LR nest. 
The protein of C11orf54 exists as a monomer in solution. The protein assumes a globular shape of 20 beta strands and 4 alpha helices, containing 9 antiparallel beta strands forming a beta screw region. The β-screw region of C11orf54 has structural similarity to the cyclic adenosine 3′,5′-monophosphate (cAMP) binding domain of the regulatory subunit of protein kinase A. A zinc ion is bound to the HxHxxxxxxxxxH motif found in the sequence. 
The protein Ester Hydrolase C11orf54 has many orthologs (see table.) It is highly conserved (60-100% identity) in mammals, reptiles, birds, and fish. The protein is moderately conserved (30-59.99% identity) in invertebrates, amphibia, Cnidaria, Mollusca, fungi and bacteria. It is not conserved in archaea. The most distant orthologs are bacteria. Figure 2 shows the unrooted phylogenetic tree of a few of C11orf54’s orthologs.
C11orf54's coordination with a zinc ion through three histidines and an acetate anion is likely to point to a function of the protein being an enzymatic reaction as an ester hydrolase. The protein has a high turnover number when reacted with p-nitrophenyl acetate (0.042 sec−1) as compared to a 1 sec−1 turnover rate found in another enzyme (bovine carbonic anhydrase II) that reacts with p-nitrophenyl acetate. 
^Briesemeister S, Rahnenführer J, Kohlbacher O (2010). "Going from where to why–interpretable prediction of protein subcellular localization". Bioinformatics (Oxford, England). 26 (9): 1232–8. doi:10.1093/bioinformatics/btq115. PMID20299325.
^Blom N, Gammeltoft S, Brunak S (1999). "Sequence and structure-based prediction of eukaryotic protein phosphorylation sites". Journal of Molecular Biology. 294 (5): 1351–62. doi:10.1006/jmbi.1999.3310. PMID10600390.
^Gupta R, Brunak S (2002). "Prediction of glycosylation across the human proteome and the correlation to protein function". Pacific Symposium on Biocomputing. Pacific Symposium on Biocomputing: 310–22. PMID11928486.
^Uhlén M, Fagerberg L, Hallström BM, Lindskog C, Oksvold P, Mardinoglu A, et al. (January 2015). "Proteomics. Tissue-based map of the human proteome". Science. 347 (6220): 1260419. doi:10.1126/science.1260419. PMID25613900.
Maruyama K, Sugano S (January 1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene. 138 (1-2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID8125298.
Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, Suyama A, Sugano S (October 1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene. 200 (1-2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID9373149.
Rual JF, Venkatesan K, Hao T, Hirozane-Kishikawa T, Dricot A, Li N, Berriz GF, Gibbons FD, Dreze M, Ayivi-Guedehoussou N, Klitgord N, Simon C, Boxem M, Milstein S, Rosenberg J, Goldberg DS, Zhang LV, Wong SL, Franklin G, Li S, Albala JS, Lim J, Fraughton C, Llamosas E, Cevik S, Bex C, Lamesch P, Sikorski RS, Vandenhaute J, Zoghbi HY, Smolyar A, Bosak S, Sequerra R, Doucette-Stamm L, Cusick ME, Hill DE, Roth FP, Vidal M (October 2005). "Towards a proteome-scale map of the human protein-protein interaction network". Nature. 437 (7062): 1173–8. doi:10.1038/nature04209. PMID16189514.