Abstract:
Background: Eleven cysteine cathepsins have been identified in human, Cathepsin B, C, F, H,
K, L, O, S, V, X and W. Studies related to their specific functions, regulation and distribution
patterns in tissues have not been fully studied to understand their biochemical implications in
human physiology. Molecular characterization including expression and recombinant
production of them in bacterial expression systems is an effective way of understanding them.
Objectives: To identify research gaps present in molecular structural characterization studies of
human cysteine cathepsins highlighting the importance of investigating them to promote health.
Methodology: This review focused on molecular structural characterization studies that have
been done so far based on in vitro expression of genes encoding for human cysteine cathepsins
in Escherichia coli expression systems. Nearly 50 related papers were found as published
literature using keywords cysteine cathepsins, expression and E. coli in global databases such as
the Google Scholar, PUBMED and NCBI and were analysed.
Results: It was seen that all cathepsins except for K, C, H, X and W have been expressed in
bacterial expression systems, the majority in E. coli BL21(DE3) pLysS host via pET3 expression
vector to understand cellular behaviour. In most cases, the substrate used to validate the
enzymatic activity of the recombinant enzyme was a cysteine residue along with a benzyloxy carbonyl salt such as benzyloxycarbonyl-L-phenylalanyl-L-arginine-7-amido-4-
rnethylcoumarln. No literature indicated that cathepsins K, C, H, X and W to have been
characterized on any molecular basis.
Conclusions: It is concluded that certain important research gaps such as precise validation of
the recombinant cysteine cathepsin produced needs to be attended to by investigating into
specific substrates utilized by each enzyme. In addition, mass production of these enzymes have
to be facilitated by optimizing their recombinant production efficiency, in order for them to be
incorporated into biopharmaceuticals productively.
