Biology:Tripeptidyl peptidase I

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Short description: Protein-coding gene in the species Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

Tripeptidyl-peptidase 1, also known as Lysosomal pepstatin-insensitive protease, is an enzyme that in humans is encoded by the TPP1 gene.[1][2] TPP1 should not be confused with the TPP1 shelterin protein which protects telomeres and is encoded by the ACD gene.[3] Mutations in the TPP1 gene leads to late infantile neuronal ceroid lipofuscinosis.[4]

Structure

Gene

The human gene TPP1 encodes a member of the sedolisin family of serine proteases. The human gene has 13 exons and locates at the chromosome band 11p15.[2]

Protein

The human TPP1 is 61kDa in size and composed of 563 amino acids. An isoform of 34.5kDa and 320 amino acids is generated by alternative splicing and a peptide fragment of 1-243 amino acid is missing.[5] TPP1 contains a globular structure with a subtilisin-like fold, a Ser475-Glu272-Asp360 catalytic triad. It also contains an octahedrally coordinated Ca2+-binding site that are characteristic features of the S53 sedolisin family of peptidases. Unlike other S53 peptidases, it has steric constraints on the P4 substrate pocket, which might contribute to its preferential cleavage of tripeptides from the unsubstituted N-terminus of proteins. Two alternative conformations of the catalytic Asp276 are associated with the activation status of TPP1.[6]

Function

High expression of TPP1 is found in bone marrow, placenta, lung, pineal and lymphocytes. The protease functions in the lysosome to cleave N-terminal tripeptides from substrates and has weaker endopeptidase activity. It is synthesized as a catalytically inactive enzyme which is activated and autoproteolyzed upon acidification.

Clinical significance

The neuronal ceroid lipofuscinoses (NCLs) are a group of inherited neurodegenerative disorders with pathological phenotypes that auto fluorescent lipopigments present in neurons and other cell types. Over the past two decades, accumulating evidences indicates that NCLs are caused by mutations in eight different genes, including genes encoding several soluble proteins (cathepsin D, PPT1, and TPP1).[7] Mutations of gene TPP1 result in late-infantile neuronal ceroid lipofuscinosis which is associated with the failure to degrade specific neuropeptides and a subunit of ATP synthase in the lysosome.[8] Mutations in the TPP1 gene lead to late infantile neuronal ceroid lipofuscinosis, a fatal neurodegenerative disease of childhood.[6] It has been demonstrated that a single injection of intravitreal implantation of autologous bone marrow derived stem cells transduced with a TPP1 expression construct at an early stage in the disease progression could substantially inhibit the development of disease-related retinal function deficits and structural changes. This result implies that ex vivo gene therapy using autologous stem cells may be an effective means of achieving sustained delivery of therapeutic compounds to tissues such as the retina for which systemic administration would be ineffective.[9]


References

  1. ↑ "Structural organization and sequence of CLN2, the defective gene in classical late infantile neuronal ceroid lipofuscinosis". Genomics 50 (2): 206–12. June 1998. doi:10.1006/geno.1998.5328. PMID 9653647. 
  2. ↑ 2.0 2.1 "Entrez Gene: TPP1 tripeptidyl peptidase I". https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1200. 
  3. ↑ "ACD ACD, shelterin complex subunit and telomerase recruitment factor [Homo sapiens (human) - Gene - NCBI"]. https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=65057. 
  4. ↑ "[Tripeptidyl peptidase 1 deficiency in neuronal ceroid lipofuscinosis. A novel mutation]". Voprosy Medit︠s︡inskoĭ Khimii 48 (6): 594–8. Nov 2002. PMID 12698559. 
  5. ↑ "Uniprot: O14773 - TPP1_HUMAN". https://www.uniprot.org/uniprot/O14773. 
  6. ↑ 6.0 6.1 "Structure of tripeptidyl-peptidase I provides insight into the molecular basis of late infantile neuronal ceroid lipofuscinosis". The Journal of Biological Chemistry 284 (6): 3976–84. February 2009. doi:10.1074/jbc.M806947200. PMID 19038966. 
  7. ↑ "Interactions of the proteins of neuronal ceroid lipofuscinosis: clues to function". Cellular and Molecular Life Sciences 68 (3): 453–74. February 2011. doi:10.1007/s00018-010-0468-6. PMID 20680390. 
  8. ↑ "The molecular genetic basis of the neuronal ceroid lipofuscinoses". Neurological Sciences 21 (3 Suppl): S15–9. 2000. doi:10.1007/s100720070035. PMID 11073223. 
  9. ↑ "Intravitreal implantation of TPP1-transduced stem cells delays retinal degeneration in canine CLN2 neuronal ceroid lipofuscinosis". Experimental Eye Research 152: 77–87. September 2016. doi:10.1016/j.exer.2016.09.003. PMID 27637672. 

Further reading

External links



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