{"id":192874,"date":"2025-02-18T09:50:12","date_gmt":"2025-02-18T09:50:12","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=192874"},"modified":"2025-02-18T09:50:14","modified_gmt":"2025-02-18T09:50:14","slug":"calculate-kcat-in-units-of-s-1-for-the-polyphenol-oxidase","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/02\/18\/calculate-kcat-in-units-of-s-1-for-the-polyphenol-oxidase\/","title":{"rendered":"Calculate kcat in units of s-1 for the polyphenol oxidase"},"content":{"rendered":"\n<p>Calculate kcat in units of s-1 for the polyphenol oxidase, where Vmax for the reaction with the dopamine substrate is 0.36 U\u00b7min\u20131\u00b7mL\u20131 (U stands for enzyme units). The enzyme concentration is 2.0 \u00d7 10\u20132 U\u00b7mL\u20131<\/p>\n\n\n\n<p>. Entry field with incorrect answer 0.18 s-1 the tolerance is +\/-2% Your answer is incorrect. Try again.<\/p>\n\n\n\n<p>The polyphenol oxidase also acts on catechol as a substrate, with a Vmax of 0.39 U\u00b7min\u20131\u00b7mL\u20131. Assuming the same enzyme concentration, what is the kcat in s-1 for the oxidase-catalyzed catechol reaction?<\/p>\n\n\n\n<p>Entry field with incorrect answer 19.5 s-1 the tolerance is +\/-2%<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-6-color\"><strong>The Correct Answer and Explanation is :<\/strong><\/mark><\/p>\n\n\n\n<p>To calculate the <strong>kcat<\/strong> (turnover number) for the polyphenol oxidase, we use the following formula:<\/p>\n\n\n\n<p>[<br>k_{cat} = \\frac{V_{max}}{[E]}<br>]<\/p>\n\n\n\n<p>Where:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>kcat<\/strong> is the turnover number in units of s\u207b\u00b9 (per second),<\/li>\n\n\n\n<li><strong>Vmax<\/strong> is the maximum velocity of the enzyme-catalyzed reaction, in units of U\u00b7min\u207b\u00b9\u00b7mL\u207b\u00b9 (enzyme units per minute per milliliter),<\/li>\n\n\n\n<li><strong>[E]<\/strong> is the concentration of the enzyme, in units of U\u00b7mL\u207b\u00b9 (enzyme units per milliliter).<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">For the dopamine reaction:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Vmax (dopamine)<\/strong> = 0.36 U\u00b7min\u207b\u00b9\u00b7mL\u207b\u00b9,<\/li>\n\n\n\n<li><strong>[E]<\/strong> = 2.0 \u00d7 10\u207b\u00b2 U\u00b7mL\u207b\u00b9.<\/li>\n<\/ul>\n\n\n\n<p>We need to convert the units of <strong>Vmax<\/strong> from U\u00b7min\u207b\u00b9\u00b7mL\u207b\u00b9 to U\u00b7s\u207b\u00b9\u00b7mL\u207b\u00b9 by dividing by 60 (since there are 60 seconds in a minute):<\/p>\n\n\n\n<p>[<br>V_{max} (dopamine) = \\frac{0.36}{60} \\, \\text{U\u00b7s}^{-1}\u00b7\\text{mL}^{-1} = 0.006 \\, \\text{U\u00b7s}^{-1}\u00b7\\text{mL}^{-1}<br>]<\/p>\n\n\n\n<p>Now, we can calculate <strong>kcat (dopamine)<\/strong>:<\/p>\n\n\n\n<p>[<br>k_{cat} (dopamine) = \\frac{0.006}{2.0 \\times 10^{-2}} \\, \\text{s}^{-1} = 0.30 \\, \\text{s}^{-1}<br>]<\/p>\n\n\n\n<p>This value of <strong>kcat (dopamine)<\/strong> is <strong>0.30 s\u207b\u00b9<\/strong>, not 0.18 s\u207b\u00b9.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">For the catechol reaction:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Vmax (catechol)<\/strong> = 0.39 U\u00b7min\u207b\u00b9\u00b7mL\u207b\u00b9,<\/li>\n\n\n\n<li><strong>[E]<\/strong> = 2.0 \u00d7 10\u207b\u00b2 U\u00b7mL\u207b\u00b9.<\/li>\n<\/ul>\n\n\n\n<p>First, we convert the <strong>Vmax (catechol)<\/strong> from U\u00b7min\u207b\u00b9\u00b7mL\u207b\u00b9 to U\u00b7s\u207b\u00b9\u00b7mL\u207b\u00b9:<\/p>\n\n\n\n<p>[<br>V_{max} (catechol) = \\frac{0.39}{60} \\, \\text{U\u00b7s}^{-1}\u00b7\\text{mL}^{-1} = 0.0065 \\, \\text{U\u00b7s}^{-1}\u00b7\\text{mL}^{-1}<br>]<\/p>\n\n\n\n<p>Now, we can calculate <strong>kcat (catechol)<\/strong>:<\/p>\n\n\n\n<p>[<br>k_{cat} (catechol) = \\frac{0.0065}{2.0 \\times 10^{-2}} \\, \\text{s}^{-1} = 0.325 \\, \\text{s}^{-1}<br>]<\/p>\n\n\n\n<p>So, the correct value for <strong>kcat (catechol)<\/strong> is <strong>0.325 s\u207b\u00b9<\/strong>, and not 19.5 s\u207b\u00b9.<\/p>\n\n\n\n<p><strong>Conclusion<\/strong>: The calculations for <strong>kcat<\/strong> were done by converting the units of <strong>Vmax<\/strong> from per minute to per second and dividing by the enzyme concentration to obtain the turnover number.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Calculate kcat in units of s-1 for the polyphenol oxidase, where Vmax for the reaction with the dopamine substrate is 0.36 U\u00b7min\u20131\u00b7mL\u20131 (U stands for enzyme units). The enzyme concentration is 2.0 \u00d7 10\u20132 U\u00b7mL\u20131 . Entry field with incorrect answer 0.18 s-1 the tolerance is +\/-2% Your answer is incorrect. Try again. The polyphenol [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-192874","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/192874","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=192874"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/192874\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=192874"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=192874"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=192874"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}