PHARMACOGENETICS Melih O. Babaoglu Æ Turgay Ocal Æ Banu Bayar S. Oguz Kayaalp Æ Atila Bozkurt Frequency and enzyme activity of the butyrylcholinesterase K-variant in a Turkish population Received: 1 October 2003 / Accepted: 3 December 2003 / Published online: 21 January 2004 Ó Springer-Verlag 2004 Abstract Objective: Among variants of the butyrylcho- linesterase gene (BChE), the K-variant causing Ala539Thr substitution is the most common one asso- ciated with about one-third reduction in the enzyme activity. This study aimed to detect the frequency of the K-variant allele in a Turkish population sample and also to evaluate how the plasma BChE activity was influ- enced by this variant. Methods: Patients administered for elective surgery (n=77) were examined for the presence of the K allele. The enzyme activity was determined in plasma. Results: The K-variant of BChE is a common allele with a frequency of 0.266 (CI 95% 0.196–0.336) in our sample from a Turkish population. Mean enzyme activity in subjects homozygous for the K-variant was about 40% lower than other subjects. Conclusion: The frequency of the BChE K-variant was significantly higher in a Turkish population than those reported for other populations and it is associated with a diminished enzyme activity. Keywords Butyrylcholinesterase Æ K-variant Æ Pharmacogenetics Introduction The level of butyrylcholinesterase (BChE; EC 3.1.1.8) activity determines the duration of action of some short- acting muscle relaxant drugs [1, 2, 3]. Genetic variation is one of the major factors determining the activity of BChE. Many genetic variants of the butyrylcholinest- erase gene (BChE) have been described [4]. Among these, the atypical (dibucaine-resistant) (A), the fluoride- resistant (F) and many silent variants are qualitative variants [5, 6], while K, J and H variants are often referred to as quantitative variants, since individuals with these types of BChE variants have reduced amounts of effective enzyme molecules per unit volume of serum [4, 7]. The K-variant was associated with a one-third reduction in BChE activity [8] and a single nucleotide change (G1615>A) in the genomic structure of BChE [9]. The K-allele was reported to be the most common BChE variant in different populations including Caucasians [9, 10, 11]. In this study, we sought to determine the frequency of BChE K-allelic variant in a sample of Turkish popula- tion. We also investigated how the genotype is reflected on the phenotype. Materials and methods Seventy-seven unrelated subjects (43 males, 34 females) admitted to Hacettepe University Hospital for elective surgery procedures were included in the study. The cases were individuals who applied for reconstructive surgery (48 from the otorhinolaryngology clinic, 29 from various other clinics). The mean age of the male and female subjects in years (SD) were 29.0 (19.9) and 22.6 (14.1), respectively. No clinical abnormalities were evident in any subject in haemato- logical or biochemical laboratory tests (aspartate aminotransferase 12–37 U/l, alanine aminotransferase 7–56 U/l, creatinine 0.3–1.1 mg/dl). Subjects with chronic diseases, pregnancy, diseases of liver or kidney, acute infections and individuals chronically using any drugs were excluded [12]. The study protocol was approved by the Hacettepe University ethics committee, and a written informed consent was obtained from each subject prior to their participation. Blood samples for DNA isolation and detection of serum BChE activity were ob- tained from each subject. Quantitative determination of BChE activity in human serum was performed on automated clinical chemistry analysers using a commercial kit (CHE, Roche Eur J Clin Pharmacol (2004) 59: 875–877 DOI 10.1007/s00228-003-0716-x M. O. Babaoglu (&) Æ B. Bayar Æ S. O. Kayaalp Æ A. Bozkurt Department of Pharmacology, Hacettepe University Faculty of Medicine, Sihhiye, 06100 Ankara, Turkey E-mail: babaoglu@hacettepe.edu.tr Tel.: +90-312-3051087 Fax: +90-312-3105312 T. Ocal Department of Anesthesiology, Hacettepe University Faculty of Medicine, Sihhiye, 06100 Ankara, Turkey