Modified GRF (1-29), CJC-1295 no DAC
Modified Growth Releasing Factor aminos 1-29, usually referred to as Modified GRF (1-29) or “ModGRF(1-29),” also known as CJC-1295 without DAC, is a synthetic analog of the endogenous peptide signaling hormone Growth Hormone Releasing Hormone (GHRH). Endogenously produced GHRH has 44 amino acids in its chain structure. A truncated synthetic form of GHRH called Sermorelin or GRF 1-29 has 29 amino acids; Modified GRF (1-29) is further changed in that it has four substituted aminos in its chain that serve the purposes of preventing degradation and oxidation in manufacture and transport as well as in vivo, while also increasing binding affinity to the GHRH receptors.
tetrasubstitued GRF (1-29)
Modified GRF (1-29) is a synthetic modification of growth hormone releasing factor (GRF) with D-Ala, Gln, Ala, and Leu substitutions at positions 2, 8, 15, and 27 respectively. These substitutions create a much more stable peptide with the substitution at position 2 to prevent DPP-IV cleavage, position 8 to reduce asparagine rearrangement or amide hydrolysis to aspartic acid, position 15 to enhance bioactivity, and position 27 to prevent methionine oxidation.
The first 29 amino acids of GHRH were discovered to be as equally potent as its full 44 amino acid structure This fragment became known as GRF (1-29). However, due to a rapid metabolic clearance analogues of GRF (1-29) were synthesized to enhance the biological activity and reduce the rapidity of metabolic clearance. These analogues were primarily created by substituting amino acids within the peptide structure for amino acids more resistant to enzymatic cleavage. One early analogue substituted the amino acid L-alanine (abbreviated as Ala or A) at the 2nd position of the peptide structure for its optical isomer (mirror image), D-alanine (abbreviated as D-Ala). This substitution resulted in a peptide bond between D-Ala and the 3rd amino acid in the structure aspartic acid (Asp) more able to resist rapid cleavage by the enzyme dipeptidyl peptidase-4, a cleavage which had previously led to an inactive peptide fragment. This successful modification prompted the further creation of analogues with additional amino acid substitutions.
In 2005, the first specific mention of tetrasubstitued GRF (1-29) appeared in a study that used it as one of the GRF (1-29) analogue peptide structures studied. The term was used to describe the replacement of the 2nd, 8th, 15th, and 27th amino acids in the structure of GRF (1-29).
In 2008, a researcher known as DatBtrue created the term modified GRF (1-29) in place of tetrasubstitued GRF (1-29) in his public articles. Continued use of the term on public and private forums has popularized and standardized the nomenclature.
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2.Grossman A, Savage MO, Lytras N, et al. (1984). “Responses to analogues of growth hormone-releasing hormone in normal subjects, and in growth-hormone deficient children and young adults”. Clin Endocrinol. 21
3.Scarborough R, Gulyas J, Schally AV, Reeves JJ (1988). “Analogs of growth hormone-releasing hormone induce release of growth hormone in the bovine”. J Anim Sci. 66 (6): 1386–1392.
4.Soule S, King JA, Millar RP (1994). “Incorporation of D-Ala2 in growth hormone-releasing hormone-(1-29)-NH2 increases the half-life and decreases metabolic clearance in normal men”. J Clin Endocrinol Metab. 79 (4): 1208–1211.
5.Jetté L, Léger R, Thibaudeau K, Benquet C, Robitaille M, Pellerin I, Paradis V, van Wyk P, Pham K, Bridon DP (2005). “Human Growth Hormone-Releasing Factor (hGRF)1–29-Albumin Bioconjugates Activate the GRF Receptor on the Anterior Pituitary in Rats: Identification of CJC-1295 as a Long-Lasting GRF Analog”. Endocrinology. 146 (7): 3052–8.
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