(D-Leu6)-LHRH (1-8) Molecular Characteristics and Pharmacological Effects Study
1. Basic Molecular Information and Structural Features
(D-Leu6)-LHRH (1-8) is a synthetic analog of Luteinizing Hormone-Releasing Hormone (LHRH), with the CAS registration number 112642-14-5. The complete amino acid sequence of this peptide is Pyr-His-Trp-Ser-Tyr-D-Leu-Leu-Arg.
In terms of molecular composition, this peptide has a molecular weight of 1085.21 and a molecular formula of C₅₂H₇₂N₁₄O₁₂. A notable feature in its structure is the introduction of D-leucine at position six, which significantly impacts the spatial conformation and biological activity due to this non-natural amino acid modification. The N-terminal pyroglutamic acid is formed by intramolecular cyclization from glutamic acid, enhancing the peptide's resistance to aminopeptidase degradation while improving stability in physiological environments.
The theoretical calculated isoelectric point for this peptide falls within a slightly basic range, primarily due to the presence of positively charged arginine residues in its structure. The guanidine group on arginine’s side chain becomes fully protonated under physiological pH conditions, while acidic amino acids are relatively scarce; such charge distribution may influence receptor binding characteristics. It should be noted that precise measurement values for the isoelectric point require experimental determination since factors like ionic strength and pH can affect actual results.
2. Stereochemical Conformation and Structural Stability
From a stereochemical perspective, (D-Leu6)-LHRH (1-8) exhibits unique conformational features. The introduction of D-leucine disrupts the symmetry typical in traditional L-amino acid peptides, altering torsional angles along the main chain which affects overall spatial arrangement within the molecule. This conformational change could lead to two significant outcomes: it may enhance resistance against proteolytic enzymes as most have evolved specificity towards L-amino acids; conversely, it might alter binding modes with receptors resulting in different biological effects compared to natural LHRH.
Aromatic amino acids present in this molecule—tryptophan and tyrosine—provide important structural stabilization factors for the peptide. Tryptophan's indole ring and tyrosine's phenolic hydroxyl can participate in various intramolecular interactions including π–π stacking, hydrogen bonding, as well as hydrophobic interactions among others. These interactions could guide specific local secondary structures despite maintaining an overall linear configuration under solution conditions near physiological temperature (37°C). Notably close to these conditions during molecular dynamics simulations suggest that transient β-turn structures may form which could be closely related to receptor recognition processes.
3. Mechanism of Action & Receptor Interaction
As a competitive antagonist for LHRH,(D-Leu6)-LHRH(1–8)’s mechanism involves complex receptor recognition processes.Natural LHRHis a decapeptide hormone secreted by hypothalamus through binding G protein-coupled receptors(GnRHR)on anterior pituitary cell membranes activating downstream signaling pathways promoting secretion LH&FSHsynthesis . Modified(D -Le u6 ) -LR H( 18 ) retains key structural domains necessary for receptor interaction but because sixth position contains D-amino-acid modifications & truncated C-terminal ,while able bind GnR HR fails effectively induce conformational changes leading G-protein activation.This “occupy but not activate” characteristic makes it typical competitive antagonist.Molecularly,D-leucines introduction likely interferes critical transmembrane region residue interactions blocking necessary rearrangements signal transduction process . At pituitary level,this antagonistic effect manifests rapid suppression LH FSH secretion unlike agonists initial flare-up response.This trait holds clinical significance especially when quick suppression gonadotropin release needed cases assisted reproductive technology preventing premature LH surge . ###4.Pharmacological Actions Clinical Application Potential n(D -Le u6 ) -LR H(18)' s pharmacology mainly reflects regulatory function hypothalamic-pituitary-gonadal axis.By competitively blocking GnR HR,it effectively inhibits gonadotropins synthesis lowering steroid hormones levels.In male animal models,this peptide induces dose-dependent decreases testosterone levels ;in female models suppresses cyclical fluctuations estrogen progesterone .This endocrine regulation provides theoretical basis application treatment various diseases.Prostate cancer therapy reducing testosterone levels inhibits hormone-dependent tumor growth.Breast cancer treatment lower estrogen levels potentially delays tumor progression.Additionally,in treating estrogen-dependent disorders such endometriosis uterine fibroids ,this peptide also shows therapeutic potential .It’s noteworthy that compared commonly used L HR H agonists(like leuprolide,goserelin),(D – Le u6 ) – LR H(18)is advantageous acting rapidly without causing initial hormonal peaks.These properties render them more favorable certain clinical scenarios requiring urgent hormonal suppression or sensitive patient populations fluctuating hormones . n ###5.Experimental Research Formulation Properties In experimental studies,(D – Le u6 ) – LR H(18)d demonstrated good vitro activity animal trial efficacy.Vitro receptor-binding experiments reveal nanomolar affinity toward Gn R HR.In rat model subcutaneous injection leads significant declines serum LH FSH concentrations exhibiting clear dose-response relationship.The solubility characteristics affected multiple factors.Limited solubility pure water greatly improved buffered solutions(p.H range PBS).For high concentration storage solutions consider using small amounts DMSO assist dissolution however caution must be taken regarding organic solvents possibly inducing conformational changes.Long-term preservation recommended lyophilized powder stored below −20 °C avoiding repeated freeze-thaw cycles.Solution state preserved at −80 °C several months though activity gradually declines over time. n ### Six.Structure Activity Relationship Future Research Prospects Studies on(D -Le u6)L-R H(18)’ s structure–activity relationships highlight importance modifications.D-amino-acids incorporation enhances metabolic stability alters bioactive properties.Future research may focus optimizing sequences improve selectivity exploring new chemical modification methods enhance pharmacokinetic profiles developing dosage forms suitable clinical administration etc.Comparing other GnRH antagonists(such as cetrorelix ganirelix)(D -Le U 60-L RH(H )(I)) presents simpler structures providing excellent models deeper investigations into their structure-function relationships.Furthermore smaller relative molar mass offers better tissue penetration particularly valuable central nervous system action studies.As advances occur within fields molecular biology drug chemistry,(d−leU_60-L RH(H )(I)) derivatives hold promise greater roles reproductive endocrinopathies hormone dependent tumors treatments.Future translational research will need emphasize long-term safety optimal dosing regimens synergistic effects alongside alternative therapies.