Cathepsin A is an enzyme that is classified both as a cathepsin and a carboxypeptidase. In humans, it is encoded by the CTSA gene. [5]
This gene encodes a glycoprotein that associates with lysosomal enzymes beta-galactosidase and neuraminidase to form a complex of high-molecular-weight multimers. The formation of this complex provides a protective role for stability and activity. It is protective for β-galactosidase and neuraminidase. [6]
Deficiencies in this gene are linked to multiple forms of galactosialidosis. [5]
Lysosomal storage diseases are a group of over 70 rare inherited metabolic disorders that result from defects in lysosomal function. Lysosomes are sacs of enzymes within cells that digest large molecules and pass the fragments on to other parts of the cell for recycling. This process requires several critical enzymes. If one of these enzymes is defective due to a mutation, the large molecules accumulate within the cell, eventually killing it.
N(4)-(beta-N-acetylglucosaminyl)-L-asparaginase is an enzyme that in humans is encoded by the AGA gene.
N-acetylgalactosamine-6-sulfatase is an enzyme that, in humans, is encoded by the GALNS gene.
Galactosidase, beta 1, also known as GLB1, is a protein which in humans is encoded by the GLB1 gene.
GM2 ganglioside activator also known as GM2A is a protein which in humans is encoded by the GM2A gene.
Cathepsin D is a protein that in humans is encoded by the CTSD gene. This gene encodes a lysosomal aspartyl protease composed of a protein dimer of disulfide-linked heavy and light chains, both produced from a single protein precursor. Cathepsin D is an aspartic endo-protease that is ubiquitously distributed in lysosomes. The main function of cathepsin D is to degrade proteins and activate precursors of bioactive proteins in pre-lysosomal compartments. This proteinase, which is a member of the peptidase A1 family, has a specificity similar to but narrower than that of pepsin A. Transcription of the CTSD gene is initiated from several sites, including one that is a start site for an estrogen-regulated transcript. Mutations in this gene are involved in the pathogenesis of several diseases, including breast cancer and possibly Alzheimer disease. Homozygous deletion of the CTSD gene leads to early lethality in the postnatal phase. Deficiency of CTSD gene has been reported an underlying cause of neuronal ceroid lipofuscinosis (NCL).
Cathepsin L1 is a protein that in humans is encoded by the CTSL1 gene. The protein is a cysteine cathepsin, a lysosomal cysteine protease that plays a major role in intracellular protein catabolism.
Cystatin-B is a protein that in humans is encoded by the CSTB gene.
Gamma-aminobutyric acid receptor subunit beta-1 is a protein that in humans is encoded by the GABRB1 gene.
Alpha-N-acetylgalactosaminidase is an enzyme that in humans is encoded by the NAGA gene.
Lysosomal acid phosphatase is an enzyme that in humans is encoded by the ACP2 gene.
Neuroligin-3 is a protein that in humans is encoded by the NLGN3 gene.
Tetraspanin-7 is a protein that in humans is encoded by the TSPAN7 gene.
Cathepsin W is a protein that in humans is encoded by the CTSW gene.
Cathepsin F is a protein that in humans is encoded by the CTSF gene.
Sialidase-1, is a mammalian lysosomal neuraminidase enzyme which in humans is encoded by the NEU1 gene.
β-Mannosidase is an enzyme with systematic name β-D-mannoside mannohydrolase, which is in humans encoded by the MANBA gene. This enzyme catalyses the following chemical reaction
Di-N-acetylchitobiase is an enzyme that in humans is encoded by the CTBS gene.
GBA2 is the gene that encodes the enzyme non-lysosomal glucosylceramidase in humans. It has glucosylceramidase activity.
Galactosialidosis, also known as neuraminidase deficiency with beta-galactosidase deficiency, is a genetic lysosomal storage disease. It is caused by a mutation in the CTSA gene which leads to a deficiency of enzymes β-galactosidase and neuraminidase. This deficiency inhibits the lysosomes of cells from functioning properly, resulting in the accumulation of toxic matter within the cell. Hallmark symptoms include abnormal spinal structure, vision problems, coarse facial features, hearing impairment, and intellectual disability. Because galactosialidosis involves the lysosomes of all cells, it can affect various areas of the body, including the brain, eyes, bones, and muscles. Depending on the patient's age at the onset of symptoms, the disease consists of three subtypes: early infantile, late infantile, and juvenile/adult. This condition is considered rare, with most cases having been in the juvenile/adult group of patients.