[5][6][7] Prolidase is an enzyme in humans that plays a crucial role in protein metabolism and collagen recycling through the catalysis of the rate-limiting step in these chemical reactions.

[11] This metal cluster facilitates catalysis by serving as a substrate binding site, activating nucleophiles, and stabilizing the transition state.

Furthermore, prolidases are classified under a smaller family called "pita-bread" enzymes, which cleave amido-, imido-, and amidino- containing bonds.

[12] The "pita-bread" fold, containing a metal center flanked by two well-defined substrate binding pockets enabled prolidase to specifically cleave between any non-proline amino acid and proline.

[11] This dimer has a crystal structure shows two approximately symmetrical monomers that both have an N-terminal domain, made up of a six-stranded mixed β-sheet flanked by five α-helices, a helical linker, and C-terminal domain, consisting of a mixed six-stranded β-sheet flanked by four α-helices.

[14] This domain performs a "pita-bread" fold, consisting of a bimetallic active center held together by two ɑ-helices and one antiparallel β-sheet.

[8] This requirement leads to prolidase being deemed a metal-activated peptidase, a term used to describe enzymes that catalyze the hydrolysis reaction changing peptides into amino acids having increased ability through the existence of metal ions.

Collagen, the most prevalent protein in the human body, is necessary for maintaining strong connective tissues, cellular proliferation, and wound healing, among other functions.

More specifically, it is essential in catalyzing the last step of the degradation of procollagen, collagen, and other proline-containing peptides into free amino acids to be used for cellular growth.

The following mechanism shows a proposed scheme for a metal-dependent "pita-bread" enzyme with residue numbering corresponding to those found in methionine aminopeptidase from E.

After a proton is removed from the bridge between the two Mn2+ ions, the GlyPro substrate causes a conformational change as it binds to the active site.

Nitric oxide, both exogenously acquired and endogenously generated, was shown to increase prolidase activity in a time- and dose-dependent manner via phosphorylation at these serine and threonine sites.

[8] This is expected because high blood glucose leads to a decrease in collagen production and inflammatory cell generation, which depreciates wound healing ability.

[8] Furthermore, Rheumatoid Arthritis, Ankylosing spondylitis, and benign joint hypermobility syndrome have corresponded with low serum prolidase levels.

Depending on the elevated levels of serum prolidase in the blood, physicians are able to determine tumor size, stage of cancer, and prognosis, all of which help significantly in treating these diseases.

For instance, one study suggested an increase in serum prolidase levels during the initial stages of cirrhotic liver fibrosis, followed by a decrease as the disease progressed.

The reaction pathway of this enzyme is key in regulating the synthesis and degradation of collagen, a vital protein necessary for multiple aspects of the body.

[23] These phenotypical symptoms vary and may include skin ulcerations, mental retardation, splenomegaly, recurrent infections, photosensitivity, hyperkeratosis, and unusual facial appearance.

[24] Serum prolidase enzyme activity is also currently being explored as a possible, reliable marker for diseases including chronic hepatitis B and liver fibrosis.

[28] Additionally, prolidase could also serve to detect fluorine-containing organophosphorus neurotoxins, like the G-type chemical warfare agents, and could antagonize organophosphorous intoxication and protect against the effects of diisopropylfluorophosphate when encapsulated in liposomes.