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Hydroxyproline is a major component of the protein collagen, [3] comprising roughly 13.5% of mammalian collagen. Hydroxyproline and proline play key roles for collagen stability. [4] They permit the sharp twisting of the collagen helix. [5]
Hyperprolinemia type II results in proline levels in the blood between 10 and 15 times higher than normal, and high levels of a related compound called pyrroline-5-carboxylate. This rare form of the disorder may appear benign at times, [ 2 ] but often involves seizures, convulsions, and intellectual disability.
Prolidase deficiency generally becomes evident during infancy, but initial symptoms can first manifest anytime from birth to young adulthood. The condition results in a very diverse set symptoms, [3] the severity of which can vary significantly between patients, depending on the degree to which prolidase activity is hampered by the individual underlying mutation(s) in each case.
In enzymology, a 4-hydroxyproline epimerase (EC 5.1.1.8) is an enzyme that catalyzes the chemical reaction trans -4-hydroxy-L-proline ⇌ {\displaystyle \rightleftharpoons } cis -4-hydroxy-D-proline Hence, this enzyme has one substrate , trans-4-hydroxy-L-proline , and one product , cis-4-hydroxy-D-proline .
Two tyrosines separated by a single amino acid, typically valine or another tyrosine, form a short intra-molecular diphenylether crosslink. [11] This can be crosslinked further by the enzyme extensin peroxidase [12] [13] [14] to form an inter-molecular bridge between extensin molecules and thus form networks and sheets.
Iminoglycinuria is an autosomal recessive [4] disorder of renal tubular transport affecting reabsorption of the amino acid glycine, and the imino acids proline and hydroxyproline. [4] [5] This results in excess urinary excretion of all three acids (-uria denotes "in the urine"). [6]
In nature, proline, hydroxyproline, pipecolic acid and sarcosine are well-known secondary amino acids. Proline is the only proteinogenic secondary amino acids. Other secondary amino acids are non-proteinogenic amino acids. In protein, hydroxyproline is incorporated into protein by hydroxylation of proline.
The systematic name of this enzyme class is UDP-N-acetyl-D-glucosamine:[Skp1-protein]-hydroxyproline N-acetyl-D-glucosaminyl-transferase. Other names in common use include Skp1-HyPro GlcNAc-transferase , UDP-N-acetylglucosamine (GlcNAc):hydroxyproline polypeptide , GlcNAc-transferase , UDP-GlcNAc:Skp1-hydroxyproline GlcNAc-transferase , and UDP ...