Long-term outcomes of surgical repair for corrected transposition of the great arteries.

BACKGROUND: This study investigated the long-term outcomes of physiological and anatomical repair for corrected transposition of the great arteries and double outlet right ventricle with discordant atrioventricular connection. METHODS: This single-center retrospective study included 146 patients who underwent biventricular repair of corrected transposition of the great arteries or double outlet right ventricle with discordant atrioventricular connections from 1972 to 2023. Survival rate, freedom from reoperation, NYHA classification and incidence of systemic ventricular dysfunction in the long-term were compared between physiological repair group (PR group) and anatomical repair group (AR group). RESULTS: PR group consisted of 55 patients with median age at repair of 10.3 years. Thirty-one patients underwent conventional Rastelli procedure and 24 patients underwent atrial and/or ventricular septal defect closure. AR group consisted of 91 patients with median age at repair of 5.8 years. Seventy-two patients underwent atrial switch plus Rastelli procedure and 19 patients underwent atrial plus arterial switch operation. The 30-year survival was 63.5% in PR group and 72.3% in AR group (p=0.448). The 30-year freedom from reoperation was 71.9% in PR group and 62.2% in AR group (p=0.220). There was a significant difference in incidence of systemic ventricular dysfunction between the groups (87.5% in PR group and 35.3% in AR group: p<0.001) and long-term survivors' NYHA classification (mean NYHA class of 1.9 in PR group and 1.5 in AR group: p=0.009). CONCLUSIONS: The systemic ventricular function and general status in the long-term were significantly better in anatomical repair patients, suggesting the potential advantage of anatomical repair.

Tricuspid valve replacement provides better long-term survival and tricuspid valve function than repair in patients with systemic right ventricle.

Objective: The purpose of this study is to compare the long-term outcomes of 2 different tricuspid surgeries including valvuloplasty and replacement for significant tricuspid regurgitation in patients with systemic right ventricle. Method: This is a retrospective study of 34 patients with dextro-transposition of the great arteries or levo-transposition of the great arteries with biventricular circulation and systemic right ventricle undergoing tricuspid valve surgery between April 1979 and April 2022. Patients were divided into 2 groups based on the procedure: tricuspid valvuloplasty (n = 11) and tricuspid valve replacement (n = 23). These groups were compared in terms of survival, tricuspid valve dysfunction, and tricuspid valve-related reoperation. Results: There was no significant difference between the groups in operative age, body weight, the proportion of dextro-transposition of the great arteries, Ebstein-like tricuspid dysplasia, and preoperative right ventricular volume/function. During the median follow-up of 9.7 years, there was 1 early death (tricuspid valvuloplasty group) and 4 late deaths (3 in tricuspid valvuloplasty group and 1 in tricuspid valve replacement group). There were 7 tricuspid valve dysfunctions, including 6 significant tricuspid regurgitations in the tricuspid valvuloplasty group and 1 prosthetic valve dysfunction in the tricuspid valve replacement group, and 4 tricuspid valve-related reoperations (3 in the tricuspid valvuloplasty group and 1 in the tricuspid valve replacement group) were performed. There were significant differences between the groups in survival (tricuspid valvuloplasty vs tricuspid valve replacement: 72.7 vs 94.7% at 10 years after surgery, P = .0328) and cumulative incidence of tricuspid valve dysfunction at 10 years after tricuspid surgery (tricuspid valvuloplasty vs tricuspid valve replacement: 27.3% vs 0%, P = .0121). Conclusions: Tricuspid valve replacement provided better long-term survival and tricuspid function in patients with systemic right ventricle compared with tricuspid valvuloplasty.

Acute onset of ornithine transcarbamylase deficiency after total anomalous pulmonary venous connection repair to a 2-day-old neonate.

Ornithine transcarbamylase deficiency is an X-linked disorder which results in the accumulation of ammonia causing irritability and vomiting. Acute hyperammonemia requires rapid and intensive intervention. However, as those clinical features are non-specific and commonly seen in peri-operative situation, ornithine transcarbamylase deficiency could be difficult to diagnose prior to and post-emergency cardiac surgery. We report a 2-day-old male neonate who was diagnosed with ornithine transcarbamylase deficiency presenting hyperammonemia and severe heart failure after total anomalous pulmonary venous connection repair.

A new nomogram of urinary flow rate and volume based on multiple measurements per healthy adult Japanese men using a portable uroflowmeter (P-Flowdiary®).

BACKGROUND: To develop a nomogram of urinary volume and flow based on the data of Japanese men without lower urinary tract symptoms and multiple flows per participant whose characteristics were clear. METHODS: Overall, 101 Japanese male volunteers without lower urinary tract symptoms aged between 20 and 59 years were enrolled. A portable uroflowmeter (P-Flowdiary®) was used to record urinary information (flow rate and volume) for 2 successive days. The model (quadratic, linear, or logarithmic regression) most fit for the relationship between maximum flow rate and voided volume was determined. The maximum flow rate at > 150 mL was compared among the 20-29-, 30-39-, 40-49-, and 50-59-year age groups. Nomograms appropriate for the age groups were created. RESULTS: The mean age, International Prostate Symptom Score, and Overactive Bladder Symptom Score were 38.5 years, 0.42, and 0.24, respectively. The quadratic regression model was the most fit because its mean coefficient determination was 0.93 ± 0.06. The mean maximum flow rate was significantly lower in the 50-59-year age group (21.8 ± 5.05 mL/s, P < 0.01) than in the younger groups (24.14 ± 4.94, 24.05 ± 6.99, and 24.64 ± 5.72 mL/s). The 2 nomograms are Y = 28.99 {1 - exp(- 0.01 × X)} and Y = 25.67 {1 - exp(- 0.01 × X)} for the 20-49- and 50-59-year age groups, respectively. CONCLUSIONS: The nomogram can predict maximum flow rate based on voided volume in Japanese men aged 20-59 years without lower urinary tract symptoms.

Surgical Outcomes in Children With Partial and Transitional Atrioventricular Septal Defect.

BACKGROUND: This study aimed to evaluate the long-term outcomes of partial and transitional atrioventricular septal defect repair, focusing on left atrioventricular valve reoperation. METHODS: We conducted a retrospective review of 104 children who underwent partial or transitional atrioventricular septal defect repair between August 1983 and January 2021. The major outcomes included patient survival and left atrioventricular valve reoperation. RESULTS: Median age at repair was 4.0 (0.1-17.0) years, with 17 patients being infants (age ≤ 1 year; 16.3%). All but eight patients (92.3%) underwent left atrioventricular valve cleft closure. After initial repair, there were 18 cases of moderate-to-severe left atrioventricular valve regurgitation (17.3%). Three in-hospital deaths (2.9%) and four late deaths (3.8%) occurred. At follow-up (median 14.3 years), actuarial survival was 95.1% and 93.0% at 1 and 20 years, respectively, and 16 patients (15.4%) had undergone a total of 19 left atrioventricular valve reoperations. Initial repair performed during infancy was associated with significantly higher mortality than a repair performed after infancy (35.3% vs 1.5%, P < .01, hazard ratio = 26.4). On multivariable analysis, repair during infancy was associated with mortality (P < .01, hazard ratio = 27.4, 95% confidence interval = 2.7-283). Partial or no cleft closure of left atrioventricular valve (P = .03, hazard ratio = 4.7, 95% confidence interval = 1.2-18.8) and moderate-to-severe left atrioventricular valve regurgitation after repair (P < .01, hazard ratio = 9.9, 95% confidence interval = 3.0-32.2) were associated with left atrioventricular valve reoperation. CONCLUSIONS: Partial and transitional atrioventricular septal defect repair outcomes were generally satisfactory. However, repair during infancy had worse survival outcomes, and moderate-to-severe left atrioventricular valve regurgitation after a repair was associated with future left atrioventricular valve reoperation.

Utility of U-Net for the objective segmentation of the fibroglandular tissue region on clinical digital mammograms.

This study investigates the equivalence or compatibility between U-Net and visual segmentations of fibroglandular tissue regions by mammography experts for calculating the breast density and mean glandular dose (MGD). A total of 703 mediolateral oblique-view mammograms were used for segmentation. Two region types were set as the ground truth (determined visually): (1) one type included only the region where fibroglandular tissue was identifiable (called the 'dense region'); (2) the other type included the region where the fibroglandular tissue may have existed in the past, provided that apparent adipose-only parts, such as the retromammary space, are excluded (the 'diffuse region'). U-Net was trained to segment the fibroglandular tissue region with an adaptive moment estimation optimiser, five-fold cross-validated with 400 training and 100 validation mammograms, and tested with 203 mammograms. The breast density and MGD were calculated using the van Engeland and Dance formulas, respectively, and compared between U-Net and the ground truth with the Dice similarity coefficient and Bland-Altman analysis. Dice similarity coefficients between U-Net and the ground truth were 0.895 and 0.939 for the dense and diffuse regions, respectively. In the Bland-Altman analysis, no proportional or fixed errors were discovered in either the dense or diffuse region for breast density, whereas a slight proportional error was discovered in both regions for the MGD (the slopes of the regression lines were -0.0299 and -0.0443 for the dense and diffuse regions, respectively). Consequently, the U-Net and ground truth were deemed equivalent (interchangeable) for breast density and compatible (interchangeable following four simple arithmetic operations) for MGD. U-Net-based segmentation of the fibroglandular tissue region was satisfactory for both regions, providing reliable segmentation for breast density and MGD calculations. U-Net will be useful in developing a reliable individualised screening-mammography programme, instead of relying on the visual judgement of mammography experts.

Structural insights into the HBV receptor and bile acid transporter NTCP.

Around 250 million people are infected with hepatitis B virus (HBV) worldwide1, and 15 million may also carry the satellite virus hepatitis D virus (HDV), which confers even greater risk of severe liver disease2. The HBV receptor has been identified as sodium taurocholate co-transporting polypeptide (NTCP), which interacts directly with the first 48 amino acid residues of the N-myristoylated N-terminal preS1 domain of the viral large protein3. Despite the pressing need for therapeutic agents to counter HBV, the structure of NTCP remains unsolved. This 349-residue protein is closely related to human apical sodium-dependent bile acid transporter (ASBT), another member of the solute carrier family SLC10. Crystal structures have been reported of similar bile acid transporters from bacteria4,5, and these models are believed to resemble closely both NTCP and ASBT. Here we have used cryo-electron microscopy to solve the structure of NTCP bound to an antibody, clearly showing that the transporter has no equivalent of the first transmembrane helix found in other SLC10 proteins, and that the N terminus is exposed on the extracellular face. Comparison of our structure with those of related proteins indicates a common mechanism of bile acid transport, but the NTCP structure displays an additional pocket formed by residues that are known to interact with preS1, presenting new opportunities for structure-based drug design.

Surgical outcomes of reoperation after Fontan completion.

OBJECTIVES: Patients who have achieved Fontan circulation may require reoperation. We reviewed the outcomes of reoperation after Fontan completion and assessed the risk factors for poor outcomes. METHODS: This was a retrospective study of 106 patients undergoing open-heart reoperations after Fontan completion in 2003 at a single institution. RESULTS: The mean age at reoperation was 24.6 ± 8.3 years. A history of Fontan failure or end-organ dysfunction was noted in 30 patients. The reoperations included 73 total cavopulmonary connection conversions, 29 atrioventricular or semilunar valve operations (17 with total cavopulmonary connection conversions) and 4 other operations. Eight early deaths occurred. During a median follow-up of 5.5 (0.01-16.2) years, there were 3 late deaths and 9 second cardiac operations. The 10-year survival rate after reoperation was 89.8%, and the 5-year second cardiac operation-free survival was 84.3%. The 10-year survival rates were significantly lower in patients who underwent surgery before 2011 (75.8% vs 100%), had a history of Fontan failure or end-organ dysfunction (71.7% vs 97.3%), had preoperative central venous pressure >15 mmHg (64.9% vs 96.5%) and were operated on with deep hypothermic circulatory arrest (DHCA) (60.0% vs 91.3%). A history of Fontan failure or end-organ dysfunction, preoperative central venous pressure >15 mmHg and requirement of DHCA were identified as risk factors for mortality. CONCLUSIONS: Reoperation after Fontan completion resulted in excellent mid-term outcomes. A history of failed Fontan circulation and the requirement of DHCA negatively affected survival outcomes.

Impella insertion for residual aortic dissection.

Acute aortic dissection with coronary malperfusion is a life-threatening disease, resulting in demanding postoperative management. We report a successful insertion of percutaneous heart pump Impella through the intact true lumen in a patient with residual aortic dissection after the graft replacement. Careful evaluation of the access site and the Impella size selection is required.

Outcome of Pulmonary Autograft After the Ross Procedure.

BACKGROUND: The purpose of this study was to assess autograft function after the Ross procedure and to review surgical outcomes associated with autograft reoperations. METHODS: This is a retrospective study of patients undergoing the Ross procedure since 1993. Autograft function and autograft reoperation were studied. Autograft failure was defined as more than moderate autograft regurgitation or autograft dilatation to more than 50 mm diameter or z-score of more than +4 in children. One hospital death was excluded from analysis as were patients with unknown late autograft status. RESULTS: Among 75 patients analyzed, preoperative diagnosis before the Ross procedure included aortic regurgitation in 26, aortic stenosis in 19, combined lesions in 28, and 2 mechanical valve malfunctions. Median age at the Ross procedure was 12.1 (0.4-43.6) years with 44 children less than 15 years old. Six patients had greater than mild autograft regurgitation at post-Ross hospital discharge. During median follow-up of 14.9 years, there were 23 autograft failures. Eighteen autograft reoperations were performed on 17 patients (13 children), including 12 aortic valve replacements, 5 aortic root replacements (including 1 valve-sparing root replacement), and 1 Konno procedure. Freedom from autograft failure and autograft reoperation at 20 years after the Ross procedure was 52.0% and 66.3%, respectively. Multivariate analysis identified greater than mild autograft regurgitation at hospital discharge from Ross procedure as a risk factor for autograft failure (P < .01). All patients who underwent autograft reoperation survived and had good health status at a median of 6.9 years after the reoperation. CONCLUSIONS: The Ross procedure is effective in delaying prosthetic aortic valve replacement, although the time-related risk of autograft failure is a real consideration.

Right Ventricle to Pulmonary Artery Conduit With Tricuspid Expanded Polytetrafluoroethylene Valves.

BACKGROUND: Excellent outcomes of right ventricle to pulmonary artery conduits with expanded polytetrafluoroethylene (ePTFE) valves have been reported. The purpose of this study was to evaluate the outcomes of the different material conduits with tricuspid ePTFE valves. METHODS: Forty-one consecutive patients who received right ventricle to pulmonary artery conduit with tricuspid ePTFE valves for biventricular repair between April 2004 and December 2016 were studied. The conduits made of autologous pericardial roll or xenograft roll were used in 22 patients (group P) and the conduits made of ePTFE tube were used in 19 patients (group G). The conduit reoperation and the conduit dysfunction were analyzed. RESULTS: During the median follow-up of 5.8 years, no death related to the conduit was observed. There were four reoperations (three in group P and one in group G). Freedom from conduit reoperation at 5 years was 100% in both groups (P = .30). Freedom from more than moderate conduit stenosis at 5 years after operation was not significantly different between groups (46.9% in group P vs 76.3% in group G, P = .23) even though the group G conduits were significantly smaller and freedom from more than moderate conduit regurgitation at 5 years was significantly better in group G (63.3% in group P vs 94.1% in group G, P = .04). CONCLUSIONS: The conduit with ePTFE valves in the ePTFE tubes had better conduit function compared with the conduit with autologous pericardial or xenograft roll, especially in terms of conduit regurgitation.

Nucleus Accumbens-Associated Protein 1 Binds DNA Directly through the BEN Domain in a Sequence-Specific Manner.

Nucleus accumbens-associated protein 1 (NAC1) is a nuclear protein that harbors an amino-terminal BTB domain and a carboxyl-terminal BEN domain. NAC1 appears to play significant and diverse functions in cancer and stem cell biology. Here we demonstrated that the BEN domain of NAC1 is a sequence-specific DNA-binding domain. We selected the palindromic 6 bp motif ACATGT as a target sequence by using a PCR-assisted random oligonucleotide selection approach. The interaction between NAC1 and target DNA was characterized by gel shift assays, pull-down assays, isothermal titration calorimetry (ITC), chromatin-immunoprecipitation assays, and NMR chemical shifts perturbation (CSP). The solution NMR structure revealed that the BEN domain of human NAC-1 is composed of five conserved α helices and two short ß sheets, with an additional hitherto unknown N-terminal α helix. In particular, ITC clarified that there are two sequential events in the titration of the BEN domain of NAC1 into the target DNA. The ITC results were further supported by CSP data and structure analyses. Furthermore, live cell photobleaching analyses revealed that the BEN domain of NAC1 alone was unable to interact with chromatin/other proteins in cells.

Elucidation of the aberrant 3' splice site selection by cancer-associated mutations on the U2AF1.

The accurate exclusion of introns by RNA splicing is critical for the production of mature mRNA. U2AF1 binds specifically to the 3´ splice site, which includes an essential AG dinucleotide. Even a single amino acid mutation of U2AF1 can cause serious disease such as certain cancers or myelodysplastic syndromes. Here, we describe the first crystal structures of wild-type and pathogenic mutant U2AF1 complexed with target RNA, revealing the mechanism of 3´ splice site selection, and how aberrant splicing results from clinically important mutations. Unexpected features of this mechanism may assist the future development of new treatments against diseases caused by splicing errors.

Binding Properties of Split tRNA to the C-terminal Domain of Methionyl-tRNA Synthetase of Nanoarchaeum equitans.

The C-terminal domain of methionyl-tRNA synthetase (MetRS-C) from Nanoarchaeum equitans is homologous to a tRNA-binding protein consisting of 111 amino acids (Trbp111) from Aquifex aeolicus. The crystal structure of MetRS-C showed that it existed as a homodimer, and that each monomer possessed an oligonucleotide/oligosaccharide-binding fold (OB-fold). Analysis using a quartz crystal microbalance indicated that MetRS-C freshly isolated from N. equitans was bound to tRNA. However, binding of the split 3'-half tRNA species was stronger than that of the 5'-half species. The T-loop and the 3'-end regions of the split 3'-half tRNA were found to be responsible for the binding. The minimum structure for binding to MetRS-C might be a minihelix-like stem-loop with single-stranded 3'-terminus. After successive duplications of such a small hairpin structure with the assistance of a Trbp-like structure, the interaction of the T-loop region of the 3'-half with a Trbp-like structure could have been evolutionarily replaced by RNA-RNA interactions, along with many combinational tertiary interactions, to form the modern tRNA structure.

G196 epitope tag system: a novel monoclonal antibody, G196, recognizes the small, soluble peptide DLVPR with high affinity.

The recognition specificity of monoclonal antibodies (mAbs) has made mAbs among the most frequently used tools in both basic science research and in clinical diagnosis and therapies. Precise determination of the epitope allows the development of epitope tag systems to be used with recombinant proteins for various purposes. Here we describe a new family of tag derived from the epitope recognized by a highly specific mAb G196. The minimal epitope was identified as the five amino acid sequence Asp-Leu-Val-Pro-Arg. Permutation analysis was used to characterize the binding requirements of mAb G196, and the variable regions of the mAb G196 were identified and structurally analyzed by X-ray crystallography. Isothermal titration calorimetry revealed the high affinity (Kd = 1.25 nM) of the mAb G196/G196-epitope peptide interaction, and G196-tag was used to detect several recombinant cytosolic and nuclear proteins in human and yeast cells. mAb G196 is valuable for developing a new peptide tagging system for cell biology and biochemistry research.

Molecular Landscape of the Ribosome Pre-initiation Complex during mRNA Scanning: Structural Role for eIF3c and Its Control by eIF5.

During eukaryotic translation initiation, eIF3 binds the solvent-accessible side of the 40S ribosome and recruits the gate-keeper protein eIF1 and eIF5 to the decoding center. This is largely mediated by the N-terminal domain (NTD) of eIF3c, which can be divided into three parts: 3c0, 3c1, and 3c2. The N-terminal part, 3c0, binds eIF5 strongly but only weakly to the ribosome-binding surface of eIF1, whereas 3c1 and 3c2 form a stoichiometric complex with eIF1. 3c1 contacts eIF1 through Arg-53 and Leu-96, while 3c2 faces 40S protein uS15/S13, to anchor eIF1 to the scanning pre-initiation complex (PIC). We propose that the 3c0:eIF1 interaction diminishes eIF1 binding to the 40S, whereas 3c0:eIF5 interaction stabilizes the scanning PIC by precluding this inhibitory interaction. Upon start codon recognition, interactions involving eIF5, and ultimately 3c0:eIF1 association, facilitate eIF1 release. Our results reveal intricate molecular interactions within the PIC, programmed for rapid scanning-arrest at the start codon.

HotBalloon Ablation of the Pulmonary Veins for Paroxysmal AF: A Multicenter Randomized Trial in Japan.

BACKGROUND: Point-by-point catheter ablation is an established treatment for drug-refractory paroxysmal atrial fibrillation (PAF). However, it is time consuming, requires excellent technique to achieve complete pulmonary vein (PV) isolation, and is associated with severe complications. OBJECTIVES: The purpose of this study was to evaluate the safety and effectiveness of a HotBalloon ablation (HBA) compared with antiarrhythmic drug therapy (ADT) for the treatment of PAF. METHODS: A prospective multicenter randomized controlled study was conducted in Japan. Patients with symptomatic PAF refractory to antiarrhythmic drugs (Class I to IV) were randomized to HBA or ADT at a 2:1 ratio and assessed for effectiveness in a comparable 9-month follow-up period. RESULTS: A total of 100 patients in the HBA group and 43 patients in the ADT group received treatment at 17 sites. HBA procedure produced acute complete PV isolation in 98.0% (392 of 400) of the PVs and in 93.0% (93 of 100) of patients in the HBA group. The chronic success rates after the 9-month effective evaluation period were 59.0% in the HBA group (n = 100) and 4.7% in the ADT group (n = 43; p < 0.001). The incidence of major complications was 11.2% (15 of 134 patients). The incidences of PV stenosis (>70%) and transient phrenic nerve injury were 5.2% and 3.7%, respectively. The mean fluoroscopy time was 49.4 ± 26.6 min (n = 134), and the mean procedure duration was 113.9 ± 31.9 min (n = 133). CONCLUSIONS: This study demonstrates the superiority of HBA compared with ADT for treatment of patients with PAF, and a favorable safety profile.

Erythrocyte aggregation under high pressure studied by laser photometry and mathematical analysis.

The effects of hydrostatic pressure on erythrocyte aggregation have been studied by laser photometry and analysis based on a phenomenological theory. Samples were prepared by suspending swine erythrocytes in their own plasma. A high-pressure vessel consisting of a stainless-steel block with a hole to hold a sample cell and two sapphire windows to allows the passage of a He-Ne laser beam was used in the experimental setup. The suspension was stirred at 1500 rpm to disperse the erythrocytes homogeneously. Immediately after reducing the stirring rate from 1500 rpm to 300 rpm, the transmitted light intensity (I) was recorded every 10 ms under a high pressure of 40-200 MPa. The value of I increased with time (t) owing to erythrocyte aggregation. From the phenomenological theory, the equation ΔI(t)=ΔIeq[1-e(-Kt)/(1-B(1-e(-Kt)))] was derived for the change in the transmitted light intensity (ΔI) due to erythrocyte aggregation, where ΔIeq is the transmitted light intensity in the steady state, K is a time constant and B is a constant that represents the ratio of the number of interaction sites on erythrocyte aggregates at time t to that in the steady state. The observed time courses of ΔI obtained at all pressures could be closely fitted to the theoretical equation. ΔIeq roughly increased with increasing pressure. On the other hand, K and B abruptly decreased above 120 MPa. The growth rate of aggregates decreased above 120 MPa. These results suggest a change in the mechanism of erythrocyte aggregation at approximately 120 MPa. We discuss the physical meaning of the parameters.

New tyrosinase inhibitory decapeptide: Molecular insights into the role of tyrosine residues.

Tyrosinase, a rate-limiting enzyme in melanin biosynthesis, catalyzes the hydroxylation of l-tyrosine to 3,4-dihydroxy-l-phenylalanine (l-dopa) (monophenolase reaction) and the subsequent oxidation of l-dopa to l-dopaquinone (diphenolase reaction). Thus, tyrosinase inhibitors have been proposed as skin-lightening agents; however, many of the existing inhibitors cannot be widely used in the cosmetic industry due to their high cytotoxicity and instability. On the other hand, some tyrosinase inhibitory peptides have been reported as safe. In this study, we found that the peptide TH10, which has a similar sequence to the characterized inhibitory peptide P4, strongly inhibits the monophenolase reaction with a half-maximal inhibitory concentration of 102 µM. Seven of the ten amino acid residues in TH10 were identical to P4; however, TH10 possesses one N-terminal tyrosine, whereas P4 contains three tyrosine residues located at its N-terminus, center, and C-terminus. Subsequent analysis using sequence-shuffled variants indicated that the tyrosine residues located at the N-terminus and center of P4 have little to no contribution to its inhibitory activity. Furthermore, docking simulation analysis of these peptides with mushroom tyrosinase demonstrated that the active tyrosine residue was positioned close to copper ions, suggesting that TH10 and P4 bind to tyrosinase as a substrate analogue.