\documentclass[10pt,border=0pt,crop,multi=false,tikz,class=scrartcl]{standalone} \usepackage[T1]{fontenc} \usepackage{DejaVuSans} \usepackage{amsmath} \usetikzlibrary{positioning, calc}  \renewcommand*{\familydefault}{\sfdefault}   \begin{document} \begin{tikzpicture}[     >=latex,     arrow/.style={->,thick},     cat2/.style={color=blue,font=\footnotesize, minimum width=1.5cm},     cat/.style={cat2, font=\itshape\footnotesize},     every node/.style={minimum width=1cm, align=center} ] \node (d1) {Diacylglycerol or phospholipid}; \node[below=1.5cm of d1,font=\large] (d2) {Arachidonic acid}; \node[right=3cm of d2] (d22) {HPETE (hydroperoxy-\\eicosatetraenoic acid)}; \node[below=2cm of d2,font=\large] (d3) {Prostaglandin H\({}_\text{2}\) (PGH\({}_\text {2}\))}; \node[below=1.25cm of d22] (d32) {Leukotriene A\(_\text 4\)}; \node[left=1.7cm of d32] (d33) {LTB\(_4\)}; \node[below=1.25cm of d32] (d42) {Leukotriene C\(_\text 4\)}; \node[below=1cm of d42] (d52) {Leukotriene D\(_\text 4\)}; \node[below=1cm of d52] (d62) {Leukotriene E\(_\text 4\)}; \node[below=4.5cm of d3,anchor=65] (d501) {Prostacyclin\\(PGI\({}_\text2\))}; \node[below right=4.5cm and -1.5cm of d3,anchor=155] (d502) {Thromboxane\\(TXA\({}_\text2\))}; \draw[arrow] (d1) --      node[pos=.5,left,cat] {Phospho-\\lipase C}      node[pos=.5,right,cat] {Phospho-\\lipase A\({}_{\textit2}\)}      (d2); \draw[arrow] (d2) --      node[pos=.5,below,cat] {Lipooxygenase\\(FLAP, Alox5)}      (d22); \draw[arrow] (d2) --      node[pos=.5,left,cat,align=right] {PGH\({}_{\textit2}\) synthase\\ (cox--1 or cox--2 and\\ peroxidase)}     (d3); \draw [arrow] (d22) -- (d32); \draw[arrow]     (d32) ++(-1.75,.75) node (h2o) {H\(_\text 2\)O}      (h2o) to [out=-90,in=0] (d33)     (d32) -- (d33)     ; \draw[arrow]     (d32) -- node [pos=.5,above left=.15cm and .5cm] (glut1) {Glutathione}     node[pos=.5,right,cat] {Glutathione-\\S-transferase}     (d42)     (glut1) to [out=0,in=90] (d42)     ; \draw[arrow]     (d42) -- node [pos=.5,below left=.1cm and .75cm] (glut2) {Glutatmic acid}     (d52)     ; \draw [arrow] (d42) to [out=-90,in=0] (glut2); \draw [arrow] (d52) -- (d62); \draw [arrow] (d3) to [out=180,in=90] node[pos=.5,above left,cat2] {PGD\\synthase} ++(-3.25,-.75)      node [anchor=north] {PGD\(_\text 2\)}     ; \draw [arrow] (d3.south) ++(-1.75,0)      -- node[pos=.5,right,cat2,align=left] {PGE\\synthase}      ++(0,-2) node[anchor=north] (d41) {PGE\(_\text2\)}; \draw [arrow] (d41) to [out=-90,in=0] ++(-1,-1) node [anchor=east] {PGF\(_\text2\)}; \draw [arrow] (d3) -- node[pos=.5,rotate=90,cat2,below] {Prostacyclin synthase}     (d501.north -| d3); \draw [arrow] (d3.south -| d502) -- node[pos=.5,rotate=90,cat2,below] {Thromboxane synthase}     (d502); \draw [arrow] (d501) -- node[pos=.5,below,cat2] {endothelium}     ++(-2.8,0)     node[anchor=east] {6-keto-\\PGF\(_{\text1\mathrm\alpha}\)}; \draw [arrow] (d502) -- node[pos=.5,below,cat2] {platelets}     ++(2.8,0)     node[anchor=west] {Thromboxane\\(TXA\(_\text2\))}; \end{tikzpicture} \end{document}